Response to Comments for Final 

Rulemaking for Clean Alternative 

Fuel Vehicle and Engine Conversions 
Response to Comments for Final 


Rulemaking for Clean Alternative 


Fuel Vehicle and Engine Conversions 


Compliance and Innovative Strategies Division 

Office of Transportation and Air Quality 

U.S. Environmental Protection Agency 

EPA-420-R-11-002 

March 2011 
 

1. List of Commenting Organizations and Abbreviations............................................... 3
 

2. Introduction ................................................................................................................. 6
 

3. General Comments in Support of the Proposal ........................................................... 7
 

4. Comments on Proposed Definitions............................................................................ 7
 

4.1 Useful Life ........................................................................................................ 7
 

4.2 Clean Alternative Fuel ...................................................................................... 8
 

4.3 Clean Alternative Fuel Conversion Manufacturer............................................ 9
 

4.4 Model Year ..................................................................................................... 10
 

5. Comments on Proposed Requirements...................................................................... 11
 

5.1	 Applicable Emission Standards ...................................................................... 11
 

5.2	 Useful Life ...................................................................................................... 16
 

5.3	 Availability of Certification Demonstration for Outside Useful Life Vehicles
 

and Engines..................................................................................................... 16
 

5.4	 Groupings, Carry-over, Carry-across, and Emission Data Vehicle/Engine
 

Selection.......................................................................................................... 17
 

5.5	 Warranty ......................................................................................................... 21
 

5.6	 Onboard Diagnostics (OBD)........................................................................... 22
 

5.7	 Fees ................................................................................................................. 28
 

5.8	 VIN Tracking.................................................................................................. 29
 

5.9	 Vehicle and Packaging Labels........................................................................ 31
 

5.10	 Marketing........................................................................................................ 32
 

6. Small Volume Manufacturers and Small Volume Test Groups/Engine Families..... 33
 

6.1	 Small Volume Status....................................................................................... 33
 

6.2	 Change in Small Volume Status ..................................................................... 34
 

6.3	 Flexibilities for Small Volume Manufacturers and Small Volume Test 

Groups/Engine Families.................................................................................. 34
 

6.4	 Assigned Deterioration Factors (DFs) for Small Volume Manufacturers and 

Small Volume Test Groups/Engine Families ................................................. 36
 

7. Demonstration Requirements.................................................................................... 37
 

7.1 Comments Specific to Vehicle Demonstrations ............................................. 37
 

7.2 Comments Specific to Heavy-Duty Engine Demonstrations.......................... 38
 

7.3 Dual-Fuel and Mixed-Fuel Procedures........................................................... 41
 

7.4 Good Engineering Judgment........................................................................... 43
 

8. Durability Testing...................................................................................................... 44
 

9. Year End Reporting................................................................................................... 45
 

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10. Technical Amendments............................................................................................. 46
 

11. Comments on Age-based Proposal............................................................................ 47
 

11.1 General Comments on age-based proposal..................................................... 47
 

11.2 New (Certification) ......................................................................................... 48
 

11.3 Intermediate Age............................................................................................. 49
 

11.4 Outside Useful Life......................................................................................... 51
 

11.5 Outside Useful Life Subcategories ................................................................. 56
 

12. Other Comments Related to this Rulemaking........................................................... 57
 

12.1 Averaging, Banking, and Trading (ABT) ....................................................... 57
 

12.2 California Regulations .................................................................................... 58
 

12.3 Associated Costs of this Rulemaking ............................................................. 58
 

12.4 Zero Emission Components............................................................................ 59
 

12.5 Engine versus Vehicle Certification ............................................................... 60
 

12.6 Certificate Expiration...................................................................................... 60
 

12.7 Changes Affecting the Economy .................................................................... 62
 

12.8 Miscellaneous ................................................................................................. 62
 

13. Other comments received.......................................................................................... 62
 

13.1 Comments Outside the Scope of this Rulemaking ......................................... 62
 

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1. Listof Commenting Organizations and Abbreviations 

The abbreviations and annotations in these tables are used throughout this 

document to refer to various organizations that submitted written and/or oral comments 

on the proposed rulemaking. 

Table 1
 

Testimony Presented at June 23, 2010 Public Hearing
 

Organization Abbreviation Docket Document Number 

John Webster 

NatGasCar LLC 

NatGasCar EPA-HQ-OAR-2009-0299-0017 

EPA-HQ-OAR-2009-0299-0017.1 

Bob Natkin, 

American Power Group, 

Inc. 

APG EPA-HQ-OAR-2009-0299-0018 

EPA-HQ-OAR-2009-0299-0018.1 

Giedrius Ambrozaitis 

Alliance of Automobile 

Manufacturers 

Auto Alliance EPA-HQ-OAR-2009-0299-0019 

EPA-HQ-OAR-2009-0299-0019.1 

Elio Muller 

Michael McAdams 

Gary Herwick 

Diesel 2 Gas Inc. 

Diesel 2 Gas EPA-HQ-OAR-2009-0299-0020 

EPA-HQ-OAR-2009-0299-0020.1 

John Reed 

Pete Petersen 

Omnitek Engineering 

Reed EPA-HQ-OAR-2009-0299-0021 

EPA-HQ-OAR-2009-0299-0021.1 

Chris Disher 

Flex Fuel U.S., LLC 

Flex Fuel US EPA-HQ-OAR-2009-0299-0022 

EPA-HQ-OAR-2009-0299-0022.1 

Jeffrey Clark, NGVAmerica NGVA EPA-HQ-OAR-2009-0299-0025 

EPA-HQ-OAR-2009-0299-0025.1 

EPA-HQ-OAR-2009-0299-0025.2 

Karen Hay, IMPCO 

Technologies, Inc. 

IMPCO EPA-HQ-OAR-2009-0299-0028 

Roger Galloway, BAF EPA-HQ-OAR-2009-0299-0028 

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Table 2
 

Comments Received During the Comment Period
 

Organization Abbreviation Docket Document Number 

J. P. Pickren Pickren EPA-HQ-OAR-2009-0299-0007 

EPA-HQ-OAR-2009-0299-0007.1 

J. Petkov Petkov EPA-HQ-OAR-2009-0299-0009 

Dr. John Reed, Core Power Reed EPA-HQ-OAR-2009-0299-0010 

EPA-HQ-OAR-2009-0299-0012 

EPA-HQ-OAR-2009-0299-0012.1 

EPA-HQ-OAR-2009-0299-0013 

EPA-HQ-OAR-2009-0299-0030 

E. Knauss Knauss EPA-HQ-OAR-2009-0299-0011 

Anonymous EPA-HQ-OAR-2009-0299-0014 

Certification Services 

International LLC 

CSI EPA-HQ-OAR-2009-0299-0016 

EPA-HQ-OAR-2009-0299-0016.1 

Clean Vehicle Education 

Foundation 

CVEF EPA-HQ-OAR-2009-0299-0026 

EPA-HQ-OAR-2009-0299-0026.1 

Roush Emissions 

Laboratory 

Roush EPA-HQ-OAR-2009-0299-0027 

EPA-HQ-OAR-2009-0299-0027.1 

State of Utah Utah EPA-HQ-OAR-2009-0299-0029 

EPA-HQ-OAR-2009-0299-0029.1 

T. Milton EPA-HQ-OAR-2009-0299-0031 

ConVerdant Vehicles ConVerdant EPA-HQ-OAR-2009-0299-0032 

Anonymous EPA-HQ-OAR-2009-0299-0033 

Caterpillar, Inc. Caterpillar EPA-HQ-OAR-2009-0299-0034 

EPA-HQ-OAR-2009-0299-0034.1 

EPA-HQ-OAR-2009-0299-0048 

Railroad Commission of 

Texas 

RRCT EPA-HQ-OAR-2009-0299-0035 

EPA-HQ-OAR-2009-0299-0035.1 

IMPCO Technologies, Inc. IMPCO EPA-HQ-OAR-2009-0299-0036 

EPA-HQ-OAR-2009-0299-0036.1 

NaturalDrive Partners, LLC Natural Drive EPA-HQ-OAR-2009-0299-0037 

Texas Commission on 

Environmental Quality 

TCEQ EPA-HQ-OAR-2009-0299-0039 

EPA-HQ-OAR-2009-0299-0039.1 

ALTe LLC ALTe EPA-HQ-OAR-2009-0299-0040 

EPA-HQ-OAR-2009-0299-0040.1 

National Truck Equipment 

Association 

NTEA EPA-HQ-OAR-2009-0299-0042 

EPA-HQ-OAR-2009-0299-0042.1 

National Propane Gas 

Association 

NPGA EPA-HQ-OAR-2009-0299-0043 

EPA-HQ-OAR-2009-0299-0043.1 

4
 
 

Alliance of Automobile 

Manufacturers 

Auto Alliance EPA-HQ-OAR-2009-0299-0044 

EPA-HQ-OAR-2009-0299-0044.1 

American Power Group, 

Inc. 

APG EPA-HQ-OAR-2009-0299-0015 

EPA-HQ-OAR-2009-0299-0045 

EPA-HQ-OAR-2009-0299-0045.1 

R.W. Wallace Wallace EPA-HQ-OAR-2009-0299-0047 

EPA-HQ-OAR-2009-0299-0047.1 

Caterpillar, Inc. Caterpillar EPA-HQ-OAR-2009-0299-0048 

Natural Gas Industry 

Transportation 

Collaborative 

The Collaborative 

EPA-HQ-OAR-2009-0299-0049 

EPA-HQ-OAR-2009-0299-0049.1 

NGVAmerica NGVA EPA-HQ-OAR-2009-0299-0050 

EPA-HQ-OAR-2009-0299-0050.1 

Y. E. Chew Chew EPA-HQ-OAR-2009-0299-0051 

EPA-HQ-OAR-2009-0299-0051.1 

Diesel 2 Gas Inc. Diesel 2 Gas EPA-HQ-OAR-2009-0299-0052 

American Alternative Fuel, 

LLC 

AAF EPA-HQ-OAR-2009-0299-0053 

EPA-HQ-OAR-2009-0299-0053.1 

Florida Department of 

Environmental Protection 

Florida DEP EPA-HQ-OAR-2009-0299-0054 

EPA-HQ-OAR-2009-0299-0054 

NatGasCar LLC NatGasCar EPA-HQ-OAR-2009-0299-0055 

Table 3
 

Comments Submitted after the Close of the Comment Period
 

Organization Abbreviation Docket Document Number 

ECO, Inc ECO EPA-HQ-OAR-2009-0299-0058 

L. Hahne EPA-HQ-OAR-2009-0299-0057 

Richard Wallace Wallace EPA-HQ-OAR-2009-0299-0059 

Jitoo Parekh EPA-HQ-OAR-2009-0299-0056 

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2. Introduction 

On May 26, 2010 (75 FR 29606), the U.S. Environmental Protection Agency 

(EPA) proposed revised regulatory criteria for gaining an exemption from the Clean Air 

Act (CAA)1 prohibition against tampering for the conversion of vehicles and engines to 

operate on a clean alternative fuel. The regulatory criteria were originally promulgated on 

September 21, 1994 (59 FR 48472), and are located in 40 CFR part 85, subpart F (“the 

subpart F regulations”). The revisions as finalized expand compliance options to include 

less burdensome demonstration requirements that will nonetheless sustain EPA's 

oversight and longstanding commitment to the environmental integrity of clean 

alternative fuel conversions. 

This new approach streamlines the regulatory process and introduces new 

flexibilities for conversion manufacturers, while ensuring that converted vehicles and 

engines retain acceptable levels of emission control. The revised program also addresses 

the uncertainty some converters may have previously experienced in determining whether 

a conversion constitutes tampering that could result in liability. EPA is revising the 

regulatory procedures in 40 CFR part 85 subpart F and part 86, to remain consistent with 

the CAA yet offer an alternative to certification for manufacturers of conversion systems 

for older vehicles or engines. The new rules reflect the concept that it is appropriate to 

treat conversion requirements differently based on vehicle or engine age. 

EPA held a public hearing on the proposed rules in Ann Arbor, Michigan, on June 

23, 2010. Oral testimony was received and recorded. A written comment period remained 

open until July 23, 2010. Tables 1, 2, and 3 above show a complete list of organizations 

that commented on the proposal, along with the abbreviations for these organizations that 

are used throughout this document. All comments and hearing testimony can be found in 

the docket for this rulemaking. Publicly available docket materials are available either 

electronically through www.regulations.gov or in hard copy at the Air and Radiation 

Docket, EPA/DC, EPA West, Room B102, 1301 Constitution Ave., NW, Washington, 

DC. See Docket ID No. EPA-HQ-OAR-2009-0299. The Public Reading Room is open 

from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The 

telephone number for the Public Reading Room is (202) 566-1744, and the telephone 

number for the Air and Radiation Docket is (202) 566-1742. 

This Response to Comments document contains a summary of all comments we 

received on the proposal along with our analysis and our response. 

1 Clean Air Act section 203; 42 U.S.C. 7522. 

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3. General Comments in Support of the Proposal 

What we proposed: 

EPA proposed to revise alternative fuel conversion regulations to simplify and 

streamline the compliance process and to create new compliance options for clean 

alternative fuel conversion manufacturers seeking an exemption from the tampering 

prohibition. The options would depend on the age of the vehicle or engine being 

converted. EPA proposed to offer new choices beyond certification for converters of 

older vehicles and engines, and to add new flexibilities for converters still required to 

obtain a certificate of conformity. 

What commenters said: 

This section contains comments in support of the overall rulemaking. Comments 

that support specific aspects of the rulemaking are incorporated into the relevant sections. 

Pickren, Milton, and Caterpillar commented that they generally support this rule. 

Pickren commented that the proposed rule is an excellent step by EPA to support more 

diverse forms of energy and to reduce reliance on sources of fuel from outside the United 

States. Petkov commented that he would support the regulations after there is a safe, 

affordable, proven and tested fuel that is readily available. 

APG commented in support of EPA efforts to simplify the rules for certification. 

Utah commented in support of the proposed revisions and encouraged EPA to 

continuously review the rule to find additional ways to streamline the process while 

maintaining a robust program. Natural Drive generally supported the rule and would like 

to see the California Air Resources Board (CARB) do something similar. NTEA 

generally supported the proposal as the current regulatory structure precludes small 

businesses from entering the conversions market. CVEF commented that they support 

and appreciate the intent of the rule and support the majority of the changes that were 

proposed. RRCT commented that this regulation makes genuine progress toward the goal 

of encouraging the development of the alternative fuel vehicle market. 

Our response: 

We appreciate the comments in support of the rule. 

4. Comments on Proposed Definitions 

4.1 Useful Life 

What we proposed: 

EPA proposed to retain the statutory and regulatory definitions of useful life. 

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What commenters said: 

Reed commented that he does not agree with EPA’s definition of useful life as it 

applies to conversions based on rebuilt and remanufactured engines. Reed stated that 

these should be treated as new vehicles and should be eligible for certification. 

Chew commented that the proposed rule would allow the useful life of a 

conversion to end at 120,000 miles, even if the vehicle had been optionally certified to 

150,000 miles by the original engine manufacturer (OEM). Chew also commented that 

EPA should allow optional certification to 150,000 miles as well as CARB's certification 

standard for certain vehicle categories at 15 years or 150,000 miles. 

Our response: 

EPA is finalizing the applicable regulatory useful life definitions as proposed to 

maintain consistency between the useful life definition for OEM vehicles and engines and 

clean alternative fuel conversions. The definitions and procedures in this rule, including 

useful life, apply to clean alternative fuel conversions as defined in the rule. Engine 

rebuild and remanufacture provisions are set forth in 40 CFR 86.004-40. 

EPA wishes to clarify that we are finalizing the determination that converted 

vehicles/engines must meet any standards applicable to the OEM, including optional 15 

year/150,000 mile standards to which the OEM vehicle/engine may have certified. See 75 

FR 29613 n. 34. 

4.2 Clean Alternative Fuel 

What we proposed: 

The proposal defined “clean alternative fuel conversion” as “any alteration of a 

motor vehicle or engine, its fueling system, or the integration of these systems, that 

allows the vehicle or engine to operate on a fuel or power source different from the fuel 

or power source for which the vehicle or engine was originally certified; and that is 

designed, constructed, and applied consistent with good engineering judgment and in 

accordance with all applicable regulations.” 

What commenters said: 

Knauss asked that we add a definition for allowable alternative compressed gas 

fuels because a number of companies are seeking to market machines that generate 

waste-derived fuel gases and are claiming that the fuel produced in the device can be 

substituted for natural gas and used in vehicles. CVEF commented that the definition of 

“clean alternative fuel,” should be reserved for fuels with demonstrated emission benefits 

and demonstrated vehicle compatibility requirements. CVEF commented that novel 

fuel/vehicle configurations should not automatically qualify for reduced certification 

requirements based just on an assertion that they constitute clean alternative fuels. 

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Our response: 

EPA is not adopting the suggestion that the definition of clean alternative fuel 

conversion should be limited to a group of fuels with proven emission benefits. These 

regulations establish protocols through which all fuel conversions, regardless of fuel type, 

may gain exemption from the tampering prohibition by demonstrating that they meet 

emission standards (new and intermediate age) or maintain or improve upon OEM 

emission levels (outside useful life). EPA believes that the requirements of the rule, and 

especially the demonstration provisions, are sufficient to ensure that only technically 

viable conversion systems will be eligible for an exemption from the tampering 

prohibition. If there is any question about the consistency or quality of a proposed 

conversion fuel, such as waste-gas derived fuels that may vary from batch to batch, EPA 

may require the converter’s demonstration to include data or other evidence to show that 

the converted vehicle/engine will comply despite potential variation in fuel properties. 

2 

The broader definition of clean alternative fuel conversion appropriately allows for future 

introduction of innovative and as-yet unknown fuels and fuel conversion systems. 

4.3 Clean Alternative Fuel Conversion Manufacturer 

What we proposed: 

The proposal defined clean alternative fuel conversion manufacturer (or 

“conversion manufacturer” or “converter”) to mean any person that manufactures, 

assembles, sells, imports, or installs a motor vehicle or engine fuel conversion for the 

purpose of use of a clean alternative fuel. 

What commenters said: 

Wallace commented that EPA should refine its definition of a “converter” as the 

current definition implies that everyone in the supply chain could be considered a 

converter which could lead to redundancy and confusion about who is responsible for 

demonstrations, notifications, and reporting. 

An anonymous commenter stated that the term “manufacturer” needs to be 

clarified to include both corporate and individual entities. 

CVEF commented that EPA should consider requiring some description of quality 

control and quality assurance procedures that kit makers will require of the entities 

actually performing conversions, including a procedure for assuring that the Quality 

Control/Quality Assurance (QC/QA) methods are complied with. 

2 http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=23319&flag=1. 

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Our response: 

EPA is finalizing the conversion manufacturer definition as proposed. The broad 

definition is intentional because any of the listed entities could meet the applicable 

requirements for a conversion system and achieve eligibility for the tampering 

exemption. However, for any given test group or engine family, EPA expects that one 

entity will function as the “manufacturer” for purposes of qualifying for an exemption. 

Should none of the listed entities follow the subpart F regulations, then all could 

potentially be liable for a tampering violation. EPA’s definition of converter ensures that 

all listed entities take responsibility for the compliance requirements and remain 

potentially liable if the requirements of the rule are not met. 

The definition of clean alternative fuel conversion manufacturer is applicable to 

both individuals and corporate entities. See CAA section 302(e) (definition of “person”). 

EPA agrees that it is important for conversion installations to be properly applied. 

Under the regulations the conversion manufacturer is responsible for its proper 

installation, even if that entity is not physically installing the conversion. EPA does not 

believe that a review of the QC/QA procedures is necessary, since the clean alternative 

fuel conversion manufacturer has a strong interest in creating products that are easily 

installed correctly and QC/QA methods that are strictly followed. 

4.4 Model Year 

What we proposed: 

The proposed regulations stated that conversion model year means the clean 

alternative fuel conversion manufacturer’s annual production period which includes 

January 1 of such calendar year. A specific model year may not include January 1 from 

the previous year or the following year. The term conversion model year means the 

calendar year if the converter has no different annual production period. 

What commenters said: 

NGVA commented that EPA should define the “model year” period differently in 

the context of systems intended to be installed on “used” vehicles or engines. The 

comments stated that that the CAA definition of ‘model year’ was intended for new 

vehicles, and that the definition limiting the model year to a period of one year that 

includes only January 1 was intended to prevent OEMs from manufacturing and selling 

vehicles in future years while claiming they are earlier model year vehicles subject to less 

stringent emissions standards. NGVA stated that this concern is not relevant in the 

context of conversions. 

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Our response: 

The CAA, EPA regulations, and EPA certification and compliance programs all 

apply the same definition to the term “model year,” which is why we are finalizing, as 

proposed, a consistent definition of conversion model year for this rule. A consistent 

definition is necessary to implement sales volume and other reporting requirements that 

are applicable to both new vehicle manufacturers and conversion manufacturers. 

5. Comments on Proposed Requirements 

5.1 Applicable Emission Standards 

What we proposed: 

EPA proposed to maintain the previous determination that converted vehicles and 

engines still within their useful life would qualify for an exemption from tampering by 

meeting the same standard that was in place for the OEM vehicle/engine. We also 

proposed that the certification demonstration for clean alternative fuel conversions must 

be based on the certification procedures, including test procedures, specified in 40 CFR 

part 86, subpart A, B and/or S and 40 CFR part1065, as applicable. Light-duty alternative 

fuel OEM vehicles and conversions are exempt from Supplemental Federal Test 

Procedure (SFTP) standards and cold carbon monoxide (CO) standards. However, SFTP 

and cold CO standards do apply for dual-fuel and mixed-fuel3 light-duty vehicles while 

the vehicle is operating on gasoline or diesel fuel. We requested comment on whether 

SFTP standards and testing would be appropriate for alternative fueled light-duty 

vehicles, including both OEM vehicles and clean alternative fuel conversions. 

What commenters said: 

Reed commented that the proposed rule did not go far enough to improve air 

quality. He stated that EPA should challenge converters to exceed the OEM standards by 

requiring conversions of 2007 and older model year heavy-duty engines to meet a 

minimum standard equivalent to the 2007 California standard, and model year (MY) 

2008 and newer vehicles and engine conversions to meet either the 2010 emission 

standards, or the current MY standard if the vehicle/engine is newer than MY2010. Reed 

commented that vehicles that meet these emission standards should then be eligible for 

certification. 

3 Mixed-fuel vehicles or engines are able to operate on either the original fuel(s) or the alternative fuel(s), 

or on a mix of the fuels. Mixed-fuel vehicles/engines are capable of combusting the different fuel types 

together in the engine. The proposal used the term “flex-fuel” to describe this type of technology. Because 

there are multiple uses and definitions of the term “flexible-fuel” in 40 CFR Part 86, in this rule we call this 

category of fuel conversion “mixed-fuel.” This definition only applies to clean alternative fuel vehicle and 

engine conversions. 

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IMPCO commented that EPA should not require SFTP or cold CO testing as it is 

not required for OEMs. IMPCO also commented that EPA should clarify/specify that 

conversions must meet any OEM greenhouse gas (GHG), carbon dioxide (CO2), or other 

Family Emission Limit (FEL) standards established by the OEM. 

NPGA commented that EPA should not add the US06 drive cycle test to the 

demonstration requirements for alternative fueled vehicles, which have been exempt from 

this test since 1996. The comments stated that EPA did not present evidence to support 

adding a US06 cycle requirement. The added test would increase the regulatory burden 

on conversion manufacturers and defeat the intent of the proposed rulemaking. NPGA 

also commented that SFTP and cold CO standards are not needed for alternative fueled 

light-duty vehicles. 

The Auto Alliance commented that EPA should require the US06 test to ensure 

adequate catalytic converter protection. The Auto Alliance also suggested that a better 

method for demonstrating compliance with this requirement would be for the converter to 

supply data showing that catalytic converter temperatures generated while the vehicle is 

being operated on the alternative fuel are the same as or less than the catalytic converter 

temperatures generated while the vehicle is being operated on the original fuel. 

Wallace commented that EPA should not require SFTP or US06 testing. Wallace 

also commented that if a converter could certify a dual-fuel vehicle to a lower standard 

on the alternative fuel, EPA should recognize the lower standard. 

Chew commented that EPA should require SFTP, US06, and high speed, 

acceleration cycles to be included in the certification demonstration for alternative fuels 

vehicles to ensure a level playing field for all dedicated, dual-fuel and mixed-fuel lightduty vehicles. Chew also asked for clarification about whether Highway Fuel Economy 

Test (HFET) test procedures and standards are required as well as the Federal Test 

Procedure (FTP). 

The Collaborative commented that they oppose unnecessary testing requirements, 

such as US06 testing and evaporative testing for dedicated compressed natural gas (CNG) 

vehicles. The comments also stated that CNG conversion kit manufacturers should be 

subject to only those tests required for OEMs that are relevant to the types of systems 

being installed. 

NGVA commented that EPA should not require US06 testing because it is not 

appropriate for EPA to impose a requirement for aftermarket manufacturers that is more 

onerous than that required for OEMs. 

Our response: 

EPA is finalizing the proposed requirement that to qualify for an exemption from 

tampering, converted vehicles and engines must meet the same standards that were in 

place for the OEM vehicle or engine, in almost all cases. Thus, the applicable standards 

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for an inside useful life clean alternative fuel conversion will be the same as the 

applicable standards for the OEM vehicle or engine, as measured over the same test 

procedures, such as FTP and HFET, where appropriate. EPA is adopting this requirement 

to ensure that there is no emissions degradation with conversion. This long-standing 

policy protects air quality and satisfies a condition necessary to grant an exemption from 

the CAA tampering prohibition. Although EPA does not think it is appropriate in this 

rulemaking to require conversions to certify to lower standards, clean alternative fuel 

conversion manufacturers may optionally demonstrate compliance with and certify inside 

useful life vehicles and engines to lower standards than were in place for the OEM. The 

process by which manufacturers may certify to a lower standard is described in the final 

rule in Clean Alternative Fuel Vehicle and Engine Conversions; Final Rule, Section 

III.F.1. Manufacturers who wish to certify a dual-fuel conversion system to a more 

stringent standard must demonstrate compliance with the lower standard on both fuels. 

EPA does not agree with Wallace’s comment that EPA should certify dual-fuel 

conversions to the lower standard on the basis of a demonstration that the conversion can 

meet the lower standard on the new alternative fuel. EPA views Wallace’s suggested 

approach as inadequate because dual-fueled vehicles, by design, are capable of operating 

on both fuels. Therefore, the vehicle could still run on the original fuel post conversion. 

Without data demonstrating the converted vehicle meets the lower standard on the 

original fuel as well as the new alternative fuel, EPA has insufficient basis for certifying 

that the dual-fuel conversion will meet the lower emission standard in use. 

Commenters did not provide data to support the concern that catalyst 

temperatures would rise as a result of combustion on typical alternative fuels. However, 

should EPA have any concerns about catalyst temperatures generated during operation on 

a new fuel, EPA may ask the converter to supply data showing that these temperatures 

remain within a range that is comparable to the catalytic converter temperatures 

generated while the vehicle is being operated on the original fuel. Since US06 and cold 

CO standards do not apply to OEM alternative fuel vehicles,4 EPA is not finalizing US06 

or cold CO testing requirements for light-duty conversions. However, any new test 

procedures or standards that apply to OEM alternative fuel vehicles/engines in the future 

would also apply to future fuel conversions, unless specifically exempted. 

IMPCO’s comments questioned whether GHG, CO2 and FEL standards apply to 

conversions. As stated previously, in almost all cases, the standards in place for an OEM 

vehicle or engine continue to apply to the converted vehicle or engine. This includes 

GHG and CO2 standards that are applicable to the OEM vehicle/engine and any FELs that 

are applicable to the OEM vehicle/engine. The applicability comment raised two issues 

unique to clean alternative fuel conversion compliance with light-duty GHG standards5 

that EPA wishes to address specifically. First, although OEMs must comply with both 

certification and fleet average GHG standards, fleet average GHG standards are not 

appropriate for clean alternative fuel conversions.

6 Consistent with our past practice, this 

was EPA's intent in the GHG rule, and the final Clean Alternative Fuel Vehicle and 

4 40 CFR 86.1810-01(i)(4). 5 75 FR 25324 (May 7, 2010). 

6 See section 12.1 of this document. 

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Engine Conversions rule adds a provision making that intent explicit. See Clean 

Alternative Fuel Vehicle and Engine Conversions; Final Rule, Section V.C. Second, the 

process by which clean alternative fuel manufacturers may demonstrate compliance with 

certification GHG standards was not addressed in the proposal. This process is spelled 

out in the final rule and is also explained below. 

OEMs comply with light-duty GHG standards by submitting GHG emissions data 

to EPA representing almost every subconfiguration in their fleet.7 Although these 

compliance provisions require extensive testing, they do not impose an additional testing 

burden because OEMs already conduct the testing to satisfy fuel economy standards and 

fuel economy labeling requirements.8 EPA considered requiring conversion 

manufacturers seeking exemption from the tampering prohibition to also submit test data 

for every subconfiguration within a conversion test group to demonstrate that the fuel 

converted vehicle meets the applicable GHG standards. However, testing at this 

granularity would be especially burdensome for an industry that is not subject to EPA 

fuel economy labeling and to which the Corporate Average Fuel Economy (CAFE) 

program does not apply. Instead, EPA believes it is reasonable to allow converters to 

submit GHG data for the emission data vehicle (EDV) within the conversion test group. 

Although EPA will allow conversion manufacturers to submit one data set to represent 

the test group, EPA expects any subconfiguration within the test group to also comply 

with the OEM nitrous oxide (N2O), methane (CH4), and CO2 standards for that 

subconfiguration, and EPA may choose any subconfiguration within the test group for 

confirmatory testing. 

The N2O and CH4 standards are clearly set forth in 40 CFR 86.1818-12(f)(1); 

however, it is more challenging to identify the CO2 or carbon-related exhaust emission 

(CREE) standard for each vehicle, since the light-duty GHG standards require that OEMs 

report actual test values for CREE. EPA evaluated several options to clearly identify the 

CREE standards to which a vehicle fuel conversion must comply. EPA considered 

requiring the conversion manufacturers to comply with the CREE values reported by the 

OEMs; however, this approach would be fundamentally different than meeting any other 

pollutant standard as it applies to fuel conversion, since all other standards generally have 

compliance “headroom” that allows for testing and production variability. For instance, 

with a specified certification emission standard, such as the Tier 2 “bins,” OEMs typically 

over-comply with the standard to give themselves some cushion for potentially higher in-use 

testing results due to emissions performance deterioration and/or normal test-to-test 

variability. However, for the OEM CO2 standards, the actual certification vehicle emission 

test results are used to calculate their fleet average. Thus, manufacturers cannot over-comply 

since the vehicle subconfiguration test result will always be the value used in determining 

their CO2 fleet average.9 For purposes of light-duty GHG OEM in-use testing, EPA 

determined it was appropriate for OEM vehicles to have a compliance margin above the 

7 Id. 

8 See 40 CFR part 600. 

9 Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy 

Standards EPA Response to Comments Document for Joint Rulemaking. EPA-420-R-10-012a (April 

2010). Page 5-339. See docket ID EPA-HQ-OAR-2009-0472-11581[1]. 

14
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

reported value:10 “The intent of the separate in-use standard, based on a 10% compliance 

factor adjustment, is to provide a reasonable margin such that vehicles are not automatically 

deemed as exceeding standards simply because of normal variability in test results.”11 For 

these same reasons, EPA believes it is appropriate to use the light-duty GHG in-use standard 

as the GHG standard that a fuel converted vehicle must meet. Therefore, EPA has determined 

that if the OEM vehicle was subject to GHG standards, fuel converted vehicles must meet 

the applicable N2O, CH4, and CO2 (CREE) subconfiguration standards that apply to the 

OEM vehicles as set forth in 40 CFR 86.1818-12(d) and 40 CFR 86.1818-12(f).12 As 

described above, the CREE standard contains a 10% adjustment factor applied to the 

initial OEM test results to account for test-to-test variability and OEM production 

margin.

13 

Similar to the OEM certification process for light-duty GHG, the clean alternative 

conversion manufacturer may use the same EDV that is used to support criteria pollutant 

testing and standards, and the CREE, N2O and CH4 test results must demonstrate that the 

converted vehicle meets the OEM N2O and CH4 standards set forth in 40 CFR 86.1818-

12(f) and the OEM subconfiguration CO2 standard set forth in 40 CFR 86.1818-12(d)14 

for the OEM subconfiguration that matches the conversion EDV. In addition, EPA may 

test or request the conversion manufacturer to test other subconfigurations within the 

conversion test group, and those results must also demonstrate compliance with the 

appropriate subconfiguration standard in 40 CFR 86.1818-12(d). 

EPA also wishes to clarify how fuel conversion manufacturers may be able to 

comply with the GHG standards if the EDV cannot meet the N20 and CH4 cap standards 

set forth in 40 CFR 86. 1818-12(f)(1). 40 CFR 86.1818-12(f)(2) sets forth an alternative 

to meeting the N2O and CH4 exhaust emission standards in 40 CFR 86.1818-12(f)(1). 

However, 40 CFR 86.1818-12(f)(2) is not available to fuel conversion manufacturers, 

since there is no GHG fleet average standard for fuel converted vehicles. Therefore, EPA 

is adding a third option, specific to fuel conversion manufacturers, that allows the same 

process set forth in 40 CFR 86.1818-12(f)(2), but that is adapted for the unique situation 

of clean alternative fuel conversion manufacturers. This alternative requires that the fuel 

conversion manufacturer determine a CREE value (including N2O and CH4) specific to 

the fuel conversion EDV, even if the OEM did not use N2O and CH4 in the CREE 

10 Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy 

Standards EPA Response to Comments Document for Joint Rulemaking. EPA-420-R-10-012a (April 

2010). Page 5-340. See docket ID EPA-HQ-OAR-2009-0472-11581[1](“EPA believes it is appropriate to 

set an in-use standard that provides a reasonable cushion for in-use variability that is not accounted for in 

the test level used to determine compliance with the fleet average. EPA proposed a factor of 10% that 

would serve this function. The factor would only be applicable to CO2 emissions, and would be applied to 

the model-level test results that would be used to establish the model-level in-use standard.”)

11 Id. 12 75 FR 25474 (May 7, 2010). If the OEM complied using the light-duty greenhouse gas fleet averaging 

option for nitrous oxide (N2O) and methane (CH4), as allowed under 40 CFR 86.1818-12(f)(2), the 

calculations of the carbon-related exhaust emissions require the input of grams/mile values for N2O and 

CH4. 13 75 FR 25473 (May 7, 2010). 14 See footnote 11. 

15
 
 

 

 

 

 

 

 

calculation. This value must meet the sub-configuration-specific in-use CO2 exhaust 

emission standard, set forth in 40 CFR 86.1818-12(d) and determined by the OEM. 

5.2	 Useful Life 

What we proposed: 

EPA proposed to leave unchanged the determination that was made in the 1994 

subpart F rulemaking that it is not appropriate to extend the useful life of a conversion 

beyond that of the original vehicle/engine. 

What commenters said: 

Caterpillar commented in support of the useful life proposal. 

Our response: 

EPA is finalizing the useful life period as proposed. We continue to agree with the 

determination made in the 1994 subpart F rulemaking and with Caterpillar’s comment 

that it is not appropriate to extend the useful life of a conversion beyond that of the 

original vehicle/engine given that conversions generally rely on many original 

components for proper operation. 

5.3	 Availability of Certification Demonstration for Outside Useful Life 

Vehicles and Engines 

What we proposed: 

EPA proposed that the certification demonstration would only be available for 

conversion of vehicles and engines within their useful life. For outside useful life vehicles 

and engines, EPA proposed an alternative demonstration and notification process. 

What commenters said: 

Reed commented that EPA should give manufacturers the opportunity to certify 

older vehicles and engines and allow rebuilders/remanufacturers to certify. 

NGVA commented that EPA should incorporate all three age-based categories 

under its certification process instead of creating a separate approval process for 

intermediate age and outside useful life vehicles. 

Our response: 

EPA is finalizing as proposed the certification demonstration and notification 

protocols for exemption of new vehicle and engine conversions from the tampering 

16
 
 

 

 

 

 

 

 

 

 

 

 

 

prohibition. Certification is also optionally available for intermediate age vehicle and 

engine conversion manufacturers. EPA is also finalizing as proposed the determination 

that certification is not available for outside useful life vehicles and engines. Certification 

is not available for vehicles and engines that have exceeded their regulatory useful life 

because the standards to which a manufacturer would certify no longer apply outside 

useful life and EPA therefore has no basis for certifying that a converted outside useful 

life vehicle/engine meets applicable standards. 

5.4	 Groupings, Carry-over, Carry-across, and Emission Data Vehicle/Engine 

Selection 

What we proposed: 

We proposed to allow conversion manufacturers to combine OEM test groups 

/engine families into larger conversion test groups/engine families, under certain 

circumstances.

15 We proposed to continue to require that the conversion test 

group/engine family be represented by a “worst case” emission data vehicle/engine 

(EDV/EDE). We also proposed to allow the conversion manufacturer to carry-over data 

if the OEM used carry-over provisions to certify the vehicle/engine being converted. The 

proposed grouping criteria would generally not allow fuel converters to combine OEM 

test groups from multiple model years, or to combine test groups from different OEMs. 

For EDV/EDE selection, we proposed that conversion manufacturers must use the 

applicable criteria to designate a conversion group, and must select a “worst case” 

EDV/EDE to represent the group for demonstration and notification purposes. 

What commenters said: 

NPGA commented in support of the grouping criteria proposal. 

APG commented in general support of the proposed test group flexibilities, but 

requested clarification on only allowing converters to combine vehicles from the ‘same 

OEM and OEM model year’ because many heavy-duty vehicles use the same engines. 

Further, APG commented that EPA should allow vehicles across model years into the 

same grouping if the engine, engine controls and emissions technology is unchanged. 

RRTC supported the proposal to broaden the criteria that are used to group 

vehicles for the purposes of certification. They further commented that using the vehicle 

with the worst gasoline emissions as the representative vehicle of the group is a 

reasonable way to ensure compliance while lowering manufacturer testing costs. 

ALTe supported the concept of broader test groups but requested additional 

flexibility, especially for conversion technologies that not only change the OEM fueling 

system but also replace most of the OEM emission control system. ALTe commented that 

conversion test groups for such technologies should be allowed to represent multiple 

15 See 75 FR 29617-29618 and 75 FR 29620-29621. 

17
 
 

 

 

 

 

 

 

 

 

 

 

 

model years and similar vehicles produced by different OEMs when such combinations 

can be supported by good engineering judgment. 

Flex Fuel US commented that converter test groups should be combined based on 

the engineering design of the fuel conversion technology, vehicle type, and engine 

classification. 

The Auto Alliance commented that EPA should not allow conversion 

manufacturers to combine multiple OEM test groups or durability groups under a single 

conversion test group. 

Wallace commented that he supports broader test groups. 

The Collaborative commented that conversions applied to vehicles/engines in the 

same weight class and at the same emissions level should be able to be represented by a 

single test group and to share a single certificate. 

NGVA commented that EPA should develop procedures to allow manufacturers 

to combine test groups of vehicles manufactured by different OEMs. 

Chew commented that EPA’s concept of test groups may need to be modified to 

address new technologies such as flexible fuel technology. 

AAF supported the proposed grouping of vehicles into larger test groups because 

grouping vehicles is an economical way to test provided that the worst case vehicle is 

used to demonstrate compliance with the standard. 

ECO commented that good engineering judgment dictates that engine family 

groupings only be allowed for test groups using the same base technology and similar 

hardware and calibration levels. 

IMPCO commented that EPA should allow manufacturers to certify intermediate 

age vehicle and engine conversions under a system similar to European regulations 

governing liquefied petroleum gas (LPG) and CNG retrofit systems. IMPCO stated that 

these regulations allow conversion system manufacturers to certify multiple vehicles and 

vehicle manufacturers by demonstrating that the same engine type and emission strategy 

is used across the board. 

EPA received comments from ConVerdant, NPGA, ECO, AAF, CSI, and 

NatGasCar that requested more flexibility to apply a single set of emission test data 

across OEM test groups spanning multiple model years. NPGA urged EPA to allow 

emissions data to carry forward (or backward) to a different model year. The comments 

stated that expanded carry-over and carry-backward of test data can result in savings in 

testing expenses and laboratory test time. 

18
 
 

 

 

ECO commented that carrying an aftermarket certification backward or forward 

(across model years) for vehicles using the same engine and emissions control system 

with minor changes seems like an application of good engineering judgment, provided 

that the testing demonstration is completed on the vehicle certified to the lowest 

standards. 

EPA also received comments regarding EDV selection. Wallace stated that the 

requirement that manufacturers choose and test a worst case EDV to represent the test 

group/engine family is too harsh a standard and that instead an average EDV should be 

allowed. NPGA commented that use of the worst-case EDV to determine emission 

compliance appears to be an equitable approach to meeting this provision of the 

regulations. The Auto Alliance commented that the selection of a worst-case EDV would 

not correct for an overly-broad grouping, as the effects of an alternative fuel on a 

vehicle’s emissions and emissions durability cannot be predicted by a single worst-case 

EDV. RRCT commented that using the worst emissions as representative of the group is 

a reasonable way to ensure compliance while lowering manufacturers’ testing costs. 

Our response: 

EPA is finalizing as proposed the criteria conversion manufacturers may use to 

combine OEM test groups. These criteria generally do not allow converters to combine 

OEM test groups from multiple model years, nor do they allow fuel converters to 

combine test groups from different OEMs. 

EPA does not agree with comments suggesting that the flexibilities should be 

further expanded for converters. Nor does EPA agree that the European approach, which 

allows a common LPG or CNG conversion kit design to be installed across many vehicle 

models, provides an adequate demonstration that post-conversion emissions will be 

maintained for a broad grouping of vehicles/engines. Emission control strategies can and 

often do differ in critical ways among manufacturers, or even among product lines of a 

single manufacturer. EPA did not receive any data or other evidence to alleviate concerns 

that these differences could result in variable emissions performance among 

vehicles/engines in the broader grouping, even if some features such as engine 

displacement are identical. For example, even among vehicles with the same engine 

displacement and cylinder configuration, other technical features, especially those 

involving variation in catalyst type, arrangement, or strategy, are likely to be different 

enough to warrant concern that the emissions will be very different after the vehicles are 

converted. Different manufacturers rarely use identical emissions-related hardware and 

software. Manufacturers may change components and strategies between model years as 

technology improves. The engine controller software will likely reflect these different 

strategies, so there is no assurance that a given conversion system will operate similarly 

or remain durable on one manufacturer’s vehicle compared to another, or on different 

model year vehicles of an individual manufacturer. EPA does not have confidence that 

significant broadening of conversion test group/engine family criteria, or expansion of 

carry-over/carry-backward/carry-across provisions can be allowed without compromising 

assurance that the conversion system will achieve equivalent emission control across the 

19
 
 

 

 

 

 

 

 

 

 

 

full test group/engine family. EPA believes the criteria for conversion test group/engine 

family combinations, which were first included in guidance on June 20, 2009 and which 

EPA is codifying in this final rule, represent an appropriate balance between reducing 

compliance burden for converters and fulfilling EPA’s responsibilities to ensure that all 

vehicles/engines remain clean. 

With respect to the APG comment about allowing engine compliance to apply to 

multiple heavy-duty chassis builders, this rule does not change current regulations under 

which OEMs certify heavy-duty highway engines to engine standards. The certified 

engine may be used in multiple heavy-duty chassis applications, with the appropriate 

chassis applications only being limited by the OEM. 

EPA disagrees with the Auto Alliance comments that the current part 86 OEM 

test group criteria should also apply to fuel converters. We believe the age-based 

approach in this rule, including flexibility to combine OEM test groups into larger 

conversion test groups, satisfies the dual objectives of maintaining environmental 

protections while offering efficiencies in testing and reporting requirements. 

EPA is not finalizing additional flexibility for carry-over and carry-across. 

Converters will continue to be able exercise the same carry-over or carry-backward 

approach as the OEM. Converters may carry-over/across test data from one model year to 

the next if the OEM did. 

EPA disagrees with the ECO comment that data can be carried across model years 

to show compliance with a less stringent emission standard, such as a Tier 2 Bin 8 

standard, when a fuel converter has demonstrated compliance to a more stringent 

standard, such as a Tier 2 Bin 5 standard for a “similar” vehicle. Given the interaction of 

the alternative fueling control system with the OEM’s test group specific emission 

control system, we believe that emission compliance is not necessarily ensured for the 

test group certified to a less stringent standard. 

EPA considered the ALTe comment regarding expanded test groups for 

conversion technologies that replace most of the OEM’s emission control system. EPA is 

finalizing the test group/engine family combination criteria as proposed. However, 

conversion manufacturers seeking exemption for technologies that replace a vehicle’s 

entire emission control system and ALL components that may affect the vehicle’s 

emission control strategy may approach the Administrator to request some additional 

flexibility for vehicle test group combinations. 

EPA does not agree that a worst case EDV/EDE is too harsh of a standard to be 

used in conjunction with expanded conversion test groups. EPA requires selection of a 

“worst case” test vehicle/engine for many regulatory requirements. This vehicle/engine is 

expected to represent the most challenging emissions compliance configuration of all the 

models it represents and gives EPA confidence that all models covered by the compliance 

grouping will meet applicable emission standards. EPA will address the Auto Alliance 

concern about the sufficiency of a worst case EDV/EDE to represent a test group by 

20
 
 

 

 

 

 

examining the fuel converter’s basis for EDV/EDE selection and EDV/EDE 

appropriateness in representing the combined test group/engine family. Should EPA have 

concerns about whether the EDV/EDE adequately represents the grouping, EPA may 

request additional data from other vehicles or engines in the group. 

5.5 Warranty 

What we proposed: 

We proposed to maintain EPA’s existing warranty policy with regard to 

alternative fuel conversions as set forth in the subpart F regulations. The general 

requirement is that conversion manufacturers must accept in-use liability for warranty 

and recall as a condition for gaining an exemption from tampering. We sought comment 

on the best way to inform consumers about the possibility that converting their vehicle or 

engine may transfer portions of their OEM warranty liability to the converter. 

What commenters said: 

NPGA commented that EPA should require a note on the vehicle label to increase 

consumers’ ability to understand the possible transfer of liability to the converter. NGVA 

commented that the final rule should provide additional guidance regarding warranty 

liability and make it unequivocally clear that a conversion does not void the original 

OEM warranty. Wallace expressed support for the NGVA proposal. Caterpillar 

recommended that EPA mandate a conversion warranty statement that clearly states that 

the conversion may affect or potentially void parts of the OEM warranty. Caterpillar also 

recommended that conversion manufacturers state that their emission warranty is not tied 

to OEM branded parts or service. Chew suggested that the warranty should be extended 

from the date of the conversion by a minimum of 2 years or 24,000 miles. Chew further 

commented that it is difficult for an end user to prove that any problems a vehicle may 

have after a conversion is as the result of that conversion. Therefore, EPA should require 

the converter and the consumer to sign a form to this effect prior to the conversion that 

outlines the responsibilities of each party. 

Our response: 

EPA is finalizing the conversions warranty provisions as proposed, which 

maintains EPA’s longstanding policy. Generally, the clean alternative fuel conversion 

manufacturer maintains liability for problems that occur as a result of conversion, while 

the OEM retains responsibility for the performance of any covered parts or systems that 

retain their original function following conversion and are unaffected by the conversion. 

Thus conversion in and of itself does not void the OEM warranty but neither are OEMs 

liable for repairs if a problem can reasonably be traced to conversion. EPA notes that 

although the commenters offered different approaches and regulatory adjustments to the 

warranty provisions, all the suggested approaches are in general agreement. All the 

commenters’ suggested approaches aim to provide additional notice to consumers of the 

potential transfer of warranty obligations between the OEM and conversion 

21
 
 

 

 

 

 

 

 

manufacturer, and oversight that warranty claims will be properly honored and 

distributed between the OEM and the conversion manufacturer. EPA agrees with those 

general goals and recognizes that consumers and converters need accurate information 

about OEM and converter warranty responsibilities. To that end, EPA has previously 

issued guidance on the topic of conversion warranties.16 EPA also plans to use its website 

to inform the public about warranty implications of vehicle/engine conversion, including 

potential confusion and even disputes over whether the OEM or the conversion 

manufacturer is responsible for any given warranty problem. 

EPA came to this decision after considering each commenter’s specific 

suggestion. In response to NPGA’s suggestion that a warranty statement be placed on the 

Vehicle Emission Control Information (VECI) label, EPA finds this added requirement 

unfeasible due to space constraints in the label. See section 5.9 for labeling comments. 

NGVA and Wallace urge EPA to make clear that a conversion does not void the OEM 

manufacturer warranty; EPA believes this is clear: the clean alternative fuel conversion 

manufacturer maintains liability for problems that occur as a result of conversion, while 

the OEM generally retains responsibility for the performance of any parts or systems that 

retain their original function following conversion and are unaffected by the conversion. 

Caterpillar would like to require additional warranty statements on conversion kits. EPA 

believes that conversion manufacturers will strive to clearly communicate warranty 

implications in the interest of satisfying their customers. Chew has suggested lengthening 

the CAA warranty time period. That comment is not germane to our request for 

comments on the best way to inform consumers about the possibility that converting their 

vehicle or engine may transfer portions of their OEM warranty liability to the converter 

and as such is outside the scope of this rulemaking. Chew also suggested that EPA 

require a conversion manufacturer and consumer to sign a written agreement 

memorializing each party’s responsibilities. EPA does not have a practical way to track 

compliance with such a requirement or to enforce against converters and consumers who 

do not sign the agreement. 

EPA again notes, for clarity, that the applicable CAA and regulatory warranties 

continue to apply to the converted vehicle/engine according to the original OEM 

warranty period. Therefore all CAA warranty requirements continue to apply to parties as 

discussed in Clean Alternative Fuel Vehicle and Engine Conversions; Final Rule, Section 

III.F.5. EPA believes this approach continues to be appropriate and reasonable. 

5.6 Onboard Diagnostics (OBD) 

What we proposed: 

EPA proposed to require converters to demonstrate that the OBD system 

continues to function properly post-conversion on any vehicle/engine for which OBD 

was required in the OEM configuration. The proposed demonstration requirements 

16 http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=23319&flag=1 and 

http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=14296&flag=1. 

22
 
 

 

 

 

 

 

 

 

 

 

differed among the three age categories. New vehicle/engine converters would need to 

complete OBD testing as has previously been required for certification. Intermediate age 

vehicle/engine converters would attest that the OBD system on the converted 

vehicle/engine continues to properly detect and identify malfunctions in all monitored 

emission-related systems or components. Additionally, EPA sought comment on whether 

a readiness flag demonstration is appropriate for intermediate age vehicles, similar to the 

Option 3 demonstration for vehicles and engines outside of useful life. For outside useful 

life vehicles and engines, we proposed the same OBD demonstration requirement as in 

the intermediate age program to prove continued compliance with OBD requirements and 

provide an attestation that the OBD system remains fully functional. The Option 3 

outside useful life program included an OBD scan tool check as described above. 

What commenters said: 

CVEF commented that the streamlined OBD demonstration EPA proposed for 

intermediate and outside useful life age categories is insufficient to ensure system 

functionality. The comments stated that claims made by kit makers and converters in the 

past have turned out to be unfounded and that the proposed OBD attestation and 

readiness demonstration is inadequate. CVEF commented that the OBD scan procedure 

proposed by EPA as part of the Option 3 demonstration may be susceptible to false 

negatives. Therefore, EPA should consider requiring a full OBD test data demonstration 

in addition to the attestation statement. 

Roush commented that EPA should require a full OBD demonstration for both the 

intermediate age and outside useful life programs, involving data submission from the 

vehicle/engine operating on the original and conversion fuels. The OBD demonstration 

Roush suggested would be accomplished on both the original and conversion fuels by 

resetting the readiness indicators and performing a series of drive cycles to demonstrate 

that all required OBD monitors run and indicate a pass/fail result. The numerical OBD 

test results and failure thresholds (Mode $06 results) would be recorded and submitted. 

The mode $06 results from each fuel type could be evaluated by EPA for adequate 

separation from the failure threshold. EPA could then infer that the similar OBD monitor 

results on both fuels in a properly functioning emissions system would likely indicate that 

the monitor results would also be similar if the emissions system should fail. For those 

diagnostics that may not have mode $06 data available, applicable engine operating 

parameter data could be recorded in its place. A statement of compliance regarding the 

readiness indicators for each monitor would be provided to EPA. The statement would 

include the Mode $06 test results, failure thresholds and any pertinent engine operating 

parameters deemed useful in demonstrating the monitors effectiveness (i.e., long- and 

short-term fuel trims). 

Utah commented that, for intermediate age and outside useful life vehicles, EPA 

should require proof of OBD functionality up front rather than after the fact, such as 

during an audit. Utah suggested applying the outside useful life Option 3 OBD scan tool 

demonstration for both intermediate age and outside useful life conversions. Utah 

commented that without such a procedure for intermediate age vehicles (and outside 

23
 
 

 

 

 

 

 

 

useful life vehicles should EPA finalize Option 1), the requirement that the installer need 

only attest that the OBD system is fully functional raises several concerns. First, the 

question of who would be required to do the attestation is not addressed. Second, EPA 

did not address the associated costs of enforcing this requirement or whether EPA would 

have adequate resources to perform audits of the installations. Lastly, EPA did not define 

what documentation would be required to verify that the conversion does not interfere 

with the OBD system. Utah commented that an Option 3-like OBD demonstration would 

provide EPA the highest assurance that the OBD system has not been tampered with and 

remains fully functional. Utah commented that EPA should adopt the good engineering 

approach in Option 1 for outside useful life vehicles that are not equipped with OBD. 

ALTe commented that EPA should give converters a time extension to comply 

with OBD requirements. The comments stated that extra time is needed to address the 

challenge of designing OBD systems for technologies such as theirs, which apply a single 

system powertrain concept to many different vehicles of different makes, model years 

and OEMs. Further, ALTe stated that converters may not have access to the OEMs’ 

proprietary OBD software. Converters must invest extensive time and capital to identify 

the numerous conditions which would cause MIL light activation. ALTe commented that 

OBD system development takes approximately two years for each major vehicle make 

and platform. 

NGVA commented that EPA should refine the criteria for an acceptable OBD 

attestation. NGVA noted that the preamble statement that an application for certification 

or approval “must contain any applicable statements of compliance or attestations and an 

OBD approval letter from the CARB or an EPA OBD approval letter if the vehicle will 

be sold only in States which have not adopted the California emissions standards” 

appears to give CARB approval too much weight. NGVA commented that the statement 

should instead require “an EPA OBD approval letter or a CARB OBD approval letter if 

the conversion systems will be sold in California or a state that only accepts CARB 

aftermarket conversions.” NGVA noted that many states have adopted CARB 

requirements for new vehicles but only a few have adopted CARB requirements for 

aftermarket conversion systems. 

Chew suggested the need for independent review of OBD data for vehicles in the 

intermediate age program if sales in a test group exceed 5,000 vehicles. He also stated 

that self attestation did not work during implementation of the Energy Star Program. 

CSI and NatGasCar commented that one OBD demonstration per manufacturer is 

sufficient and that fuel converters should be allowed to carry over an OBD demonstration 

if the OEM uses “similar” OBD family designations from one model year to the next. 

CSI, NatGasCar, and Flex Fuel US asked EPA to publish the OEM OBD groups 

so converters may determine what OEM test groups may combined when certifying 

under the new vehicle program. 

24
 
 

 

 

 

 

 

 

 

 

 

 

ECO commented that EPA should allow more OBD carry-across for fuel 

converters that are exercising good engineering judgment 

RRCT commented that EPA should require proof of OBD compliance for outside 

useful life vehicle conversions. 

AAF expressed support for requiring OBD testing for intermediate age and 

outside useful life vehicles. 

NPGA stated that conversions deemed compliant under the intermediate age 

program could have poorly designed OBD systems if attestations are not required to be 

supported by test data. 

Flex Fuel US commented that EPA should extend the use of good engineering 

judgment in lieu of requiring actual OBD data. 

The Auto Alliance suggested retaining current part 86 OBD demonstration 

requirements for all fuel converters. 

Reed commented that the readiness flag demonstration for intermediate age 

vehicles is inappropriate and that EPA should rely on state emissions testing for vehicles 

equipped with OBD. 

Our response: 

EPA is finalizing the OBD requirement as proposed for new vehicle and engine 

conversions, and is adding an OBD scan tool test to the proposed attestation requirement 

for intermediate age and outside useful life vehicles. 

EPA understands that compliance with the OBD regulations in 40 CFR part 86 

may represent the majority of the time and testing expense to certify a fuel conversion. 

The age-based proposal, which allows an alternative OBD demonstration for converters 

of older vehicles and engines, was designed to address these concerns. However, in 

designing the OBD demonstration requirements, EPA also considered the need to ensure 

that reliable and accurate emissions monitoring continues post-conversion. Fuel 

converters that qualify as small volume manufacturers or small volume test 

groups/engine families may be exempt from the durability demonstration requirements in 

place for larger manufacturers. Because the small volume durability provisions do not 

generally involve upfront submission of significant emissions durability data on the 

alternative fuel, a functional OBD system may be the primary means by which in-use 

problems in fuel converted vehicles will be detected. 

EPA believes that a proven OBD system for vehicles being fuel converted under 

the new vehicle program is important and that new vehicle and engine converters should 

be held to the current OBD compliance requirements in part 86, just as OEMs are for 

their new certification vehicles. EPA believes it prudent to maintain a level playing field 

25
 
 

 

 

 

 

 

 

 

 

 

 

for the OEMs and conversion manufacturers receiving a certificate of conformity. New 

vehicles and engines have not yet experienced deterioration and are still likely to be 

representative, for purposes of emissions, of the technical condition of the vehicle or 

engine that the OEM used for EPA certification. Thus, the certification process is suitable 

for and may be directly applied to new vehicle and engine clean alternative fuel 

conversions. EPA does not agree with comments suggesting that OBD data should be 

broadly carried-across, because OEMs may employ different OBD strategies for different 

vehicle and engine models. 

EPA agrees with Utah’s comments and other comments suggesting that an upfront OBD demonstration should be part of all three age-based programs. A properly 

functioning OBD system is essential to maintaining emissions compliance in aging 

vehicles and engines. Up-front OBD demonstrations offer a more comprehensive and 

effective approach than in-use audits do to ensuring that the OBD system functions 

properly. Therefore EPA is finalizing an OBD demonstration for intermediate age and 

outside useful life vehicles that is streamlined relative to the OBD requirements for 

certification but that is sufficiently robust to confirm that the OBD system will continue 

to work properly. In lieu of submitting OBD test data as is required for certification, 

manufacturers of clean alternative fuel conversion systems for intermediate age and 

outside useful life vehicles/engines may be able to submit an OBD scan tool report 

showing results of an OBD scan tool test procedure and attest that the OBD system 

remains fully functional in the converted vehicle/engine. The attestation must state that 

the test group/engine family converted to an alternative fuel has fully functional OBD 

systems and therefore meets the OBD requirements such as those specified in 40 CFR 86, 

subparts A and S when operating on the alternative fuel. This includes any new 

monitoring capability necessary to identify potential emission problems associated with 

the new fuel. The scan tool procedure, described in the proposal with a reference to the 

regulations in 40 CFR 85.2222, checks the status of OBD readiness monitors, checks to 

determine if the OBD malfunction indicator light (MIL) is functional (bulb check), 

checks for commanded-on MIL illumination, and records all diagnostic trouble codes if 

the MIL is illuminated. However, these regulations reference Society of Automotive 

Engineers (SAE) OBD diagnostic mode assignments that are specific to light-duty 

vehicles and light-duty trucks. In order to be clear that the OBD scan tool procedure 

described above applies to all vehicles and engines that are required to comply with OBD 

regulations, we are adding the process described in 40 CFR 85.2222 to the new subpart F 

regulations, without the specific references to the light-duty vehicle OBD procedures. 

Any scan tool that displays the supported monitors, lists their corresponding readiness 

status, and reports all emission-related pending and confirmed diagnostic trouble codes is 

considered acceptable. EPA believes requiring intermediate age and outside useful life 

fuel converters to submit a printed scan tool report following the regulations in section 40 

CFR 85.515(b)(9) and 85.520(b)(4), is sufficient to demonstrate that the OBD system is 

fully functional while operating on the alternative fuel. However, EPA may require OBD 

testing as set forth for certification if the OBD scan tool report is not sufficient to 

demonstrate proper OBD operation. An acceptable OBD demonstration under the 

intermediate age and outside useful life programs must include a printout of scan tool 

results following the fuel conversion showing that all supported monitors have been set to 

26
 
 

 

 

 

 

 

 

 

ready and that there are no pending or confirmed diagnostic trouble codes. The 

vehicle/engine identification number (VIN/EIN) must be provided with the scan tool 

report. Given the changes to the vehicle/engine resulting from the fuel conversion 

process, some monitors in the OEM OBD system may no longer be supported. For 

example, the evaporative emissions readiness monitor may need to remain unset for 

conversions in which the original evaporative emissions system is no longer functionally 

necessary. 

We recognize the concerns expressed about a lesser standard of proof relative to 

certification for the OBD system for fuel converters in the intermediate age and outside 

useful life programs, and believe the final rule provides the proper balance between the 

need for effective OBD compliance requirements and the policy goal of reducing burden 

for fuel converters seeking an exemption from tampering under either the intermediate 

age or outside useful life program. EPA disagrees with the Auto Alliance general 

comment that all fuel converted vehicles must comply with part 86 requirements, 

including OBD requirements. We believe the OBD demonstration requirements for the 

intermediate age and outside useful life programs, where certification is not required, are 

an appropriate balance for older vehicles and will ensure fully functional OBD systems. 

In response to CVEF’s concerns that an OBD scan tool procedure is inadequate, EPA 

disagrees. While full OBD testing provides a higher level of assurance that the OBD 

system works precisely within specified ranges to identify potential emissions increases, 

the OBD scan tool procedure EPA is finalizing will confirm that the OBD system is 

functional post conversion. This, together with the converter’s attestation that the system 

functions as designed and/or has been upgraded to perform functions necessary for 

monitoring emissions on the new fuel, will achieve proper monitoring of key emission 

control components or systems 

EPA appreciates the time line constraints that fuel converters face given that they 

cannot begin their demonstration activity until the OEM has introduced a certified vehicle 

into commerce. However, EPA does not wish to grant extensions in OBD compliance for 

conversion manufacturers. Manufacturers of conversion systems such as described by 

ALTe may need to design and prove-out a completely new OBD system to monitor the 

entirely different powertrain and emission control approach in the converted vehicle. It is 

especially important to demonstrate that the OBD system is fully functional in these types 

of conversions. Vehicle owners, repair shops and operators of state inspection and 

maintenance (I/M) programs rely on the OBD system to identify potential emissions 

problems. I/M programs are essential to maintaining air quality in many areas. Therefore, 

EPA believes the OBD system must be fully functional to obtain an exemption from the 

tampering prohibition under this regulation. 

In response to NGVA’s comment that the proposal gave too much weight to the 

CARB OBD process, our intention was merely to provide a summary of the existing 

requirements and flexibilities for the convenience of the reader. Please see the federal 

OBD regulations for federal OBD requirements and relevant flexibilities, such as CARB 

OBD approvals. 

27
 
 

 

 

 

 

 

 

 

 

 

 

 

EPA is not adopting differences in requirements as a function of sales volumes for 

fuel converters submitting documentation under the intermediate age or outside useful 

life programs, as suggested by Chew, since OBD serves a critical function for individual 

vehicle owners, repair shops, and air quality. 

CSI, NatGasCar, and Flex Fuel US submitted comments that OEM OBD groups 

should be made available to fuel converters when requested. Currently, OEMs provide 

this information to EPA as confidential business information. EPA is working with 

OEMs to develop an approach through which converters can have access to this 

information. 

EPA considered the Roush comment suggesting that fuel converters should 

submit scan tool data to EPA on the pre- and post- fuel converted vehicle showing 

numerical OBD test results and failure thresholds. An examination of such data could 

signal the robustness of the alternative fuel calibration by indicating whether the fuel 

converted vehicle is likely to set a diagnostic trouble code or illuminate a MIL due to lack 

of headroom between the numerical result and the failure threshold. FTP emission results, 

in combination with deterioration factors, generally result in compliance headroom, 

which is valuable to ensure full useful life compliance. EPA does not wish to require an 

additional test that requires headroom based on OBD scan tool data. Nevertheless, EPA 

encourages fuel converters to examine such OBD data for vehicles and engines of all 

ages. 

5.7 Fees 

What we proposed: 

We proposed to retain current requirements for alternative fuel converters to pay 

fees as part of the certification application process. 

What commenters said: 

Natural Drive commented that CARB imposes no fees for processing Executive 

Orders and that EPA should not impose fees on converters either. They commented that 

the proposed rulemaking would exempt fees for intermediate age vehicles so EPA should 

do so for the new vehicle category as well. Natural Drive further commented that EPA is 

“double-dipping” on alternative fuel converters because every vehicle converted has 

already had federal certification fees paid on it by the OEM. 

ALTe and NGVA commented that in addition to waiving certification fees for 

vehicles that are older than two years old, EPA should modify the certification fees 

currently charged in order to allow aftermarket manufacturers to pay these fees at the 

back end instead of upfront. Currently manufacturers must pay fees upfront based on 

expected sales. If these sales do not materialize they can request a refund. The comments 

stated that the requirement to submit fees and then later request a refund ties up valuable 

funds, which most small manufacturers cannot afford to have tied up. NGVA proposed 

28
 
 

 

 

 

 

 

 

 

 

 

 

that EPA adopt procedures to allow manufacturers the option of paying fees at the end of 

each quarter or annually based on the total number of vehicles actually sold under a 

certificate. Another approach would be to only require payment of an initial fee of $750 

at the time an application is submitted and allow the manufacturer to pay any additional 

fees quarterly or annually based on sales that have occurred. 

The Auto Alliance commented that they support the already reduced fees for 

small volume manufacturers. To further assist small volume manufacturers, EPA could 

further reduce certification fees or assign a dedicated person to assist conversion 

companies with the certification requirements and process. 

The Collaborative commented that the renewal fees should be waived if no 

significant changes to engine emissions systems have been made by the manufacturer 

from one year to the next. They also commented that fees should be allowed to be paid at 

the end of each quarter or annually based on actual vehicle sales. 

Our response: 

EPA is retaining the fees provisions as proposed. EPA already provides 

compliance support to conversion manufacturers, and has a reduced fees program for 

small entities that applies to most converters. The reduced fees program allows 

manufacturers to pay 1% of the added value of each sale multiplied by the number of 

sales.17 EPA believes that a 1% fee is a reasonable burden and is consistent with other 

small entity certification fees, such as those paid by Independent Commercial Importers 

and other small volume manufacturers. EPA is authorized to assess fees on regulated 

industry to recover all reasonable costs associated with vehicle and engine certification 

and compliance monitoring and testing. The Agency incurs costs in conducting these 

activities for conversion manufacturers, just as it does for conducting OEM certification 

and compliance. It is therefore appropriate for EPA to collect fees from conversion 

manufacturers. EPA believes that the current program which requires manufacturers to 

pay fees upfront, prior to certification is the most effective means for ensuring that fees 

are paid. That said, most converters will pay reduced fees under the new regulations. The 

intermediate age and outside useful life compliance programs do not require submission 

of fees, and the new vehicle program only requires fees to be paid upon initial 

certification. 

5.8 VIN Tracking 

What we proposed: 

We requested comment as to whether converters should submit VIN tracking 

information to EPA and whether EPA should make such information publically available. 

17 See 40 CFR 1027.120. 

29
 
 

 

 

 

What commenters said: 

IMPCO commented that VIN tracking is unnecessary and burdensome and would 

require an instant up–to–date tracking mechanism that EPA would have to update on an 

extremely frequent basis to ensure that the data are readily available. 

The Auto Alliance commented that EPA should publish a list of VINs of 

converted vehicles and make the information available to OEMs and to state I/M 

agencies. This would help ensure that these organizations are properly informed of a 

vehicle’s conversion and warranty status. The Auto Alliance further commented that it 

would not be difficult since EPA has already said it will post a list of EPA approved 

conversions that have satisfied EPA demonstration and notification requirements and are 

considered compliant. 

Wallace did not support VIN tracking. Wallace commented that such reporting is 

not needed because the parties will have the vehicle in front of them which is labeled. 

Converters ought to keep records if they choose to, and they likely will for good business 

purposes and manufacturers will never know, or need to know, specific VINs. In 

addition, Wallace commented that EPA did not adequately address the costs or benefits 

of implementing VIN tracking. 

ALTe supported VIN tracking and commented that this information should be 

available to the public for traceabililty, for use on the state level where vehicle emissions 

testing programs exist, and for purposes of informing the public that a reputable shop 

performed the conversion. ALTe stated that this approach would help to protect the 

credibility and reputation of the conversion industry and forward the goal of encouraging 

clean alternative fuel conversions and protection of the environment. 

NGVA supported making VIN and annual sales information available to the 

public and to other authorities to assist in identifying conversions. NGVA further 

commented that the final rule should clarify who has the obligation to report the VIN. 

NGVA stated that converters are in the best position to do so. 

Chew commented that EPA should make available a comprehensive and 

searchable list of conversions that notes any OBD exemptions. Converters should also 

submit VIN tracking info to EPA and make it available to state I/M programs. 

Our response: 

EPA evaluated but has decided not to finalize a VIN-tracking requirement. A 

policy that obliges EPA to track VINs would present a major administrative challenge. 

EPA does not have a practical way to implement this type of vehicle tracking system or 

to enforce against installers who do not report VINs. EPA agrees with Wallace’s 

comment that the vehicles and engine labeling requirements will be sufficient to identify 

which vehicles and engines have been converted. 

30
 
 

 

 

 

5.9 Vehicle and Packaging Labels 

What we proposed: 

EPA proposed to retain the labeling requirements contained in the subpart F 

regulations. EPA also proposed to require some additional content for the label. The 

additions would include the conversion manufacturer’s evaporative/refueling family and 

test group or engine family, as well as a statement specifying the minimum age and/or 

mileage requirements, OEM model year of vehicles, and the specific OEM test groups or 

engine families to which the conversion system is applicable. 

What commenters said: 

IMPCO comments supported keeping the existing labeling requirements with two 

suggestions: 1) allow certifying manufacturers to include the proposed or additional 

information either on the label or in marketing materials; and 2) clarify that the labels are 

meant for typical underhood usage. 

The Auto Alliance supported the existing labeling requirement and recommended 

that the label also show the converted vehicle’s estimated cruising range and the 

converted vehicle's emission certification standard. The Auto Alliance strongly 

recommended that the label should include the following statement: “OEM warranties 

will not cover damage to existing systems from damage caused by fuel conversions.” In 

addition, the Auto Alliance commented that a second identical label should be required to 

be permanently affixed on the driver door B-pillar, or glove box door or center console 

area to ensure that the consumer (or potential next purchaser) is properly informed of the 

vehicle's conversion and warranty status. 

Wallace commented that he does not agree with the Auto Alliance comments on 

labeling. 

NGVA comments supported previous labeling requirements and opposed the 

proposed new additional labeling requirements. 

Chew recommended additional information such as certification class (e.g., 

CARB LEV, ULEV) be added to the label prevent misapplication and to troubleshoot 

problems. 

Utah commented in support of the proposed labeling requirements and stated that 

the labeling information will help with proper identification of fuel converted vehicles. 

Our response: 

EPA is finalizing the labeling requirements as proposed. We understand that it 

may be challenging to fit all the information on an underhood or engine label; however, 

EPA believes that clear labeling with sufficient information will reduce the incidence of 

31
 
 

 

 

 

 

misapplication. To address concerns of space, EPA will allow the label information to be 

logically split among two labels that are both placed as close to the original VECI or 

engine label as possible. EPA does expect the labels to be permanent and able to 

withstand typical underhood operating temperatures and other environmental factors. 

EPA does not agree that the estimated cruising range should be required on a 

clean alternative fuel conversion label, since fuel economy testing is not part of EPA’s 

fuel conversion requirements. EPA does not agree that the certification standard should 

be required on the clean alternative fuel conversion label, since it already appears on the 

OEM VECI label. 

With respect to the request to include CARB vehicle classification on the VECI 

label, the CARB standards and the CARB vehicle classification are listed on OEM VECI 

labels, which must be present on any fuel conversion. 

5.10 Marketing 

What we proposed: 

We proposed that marketing material for a given conversion system must be 

consistent with vehicle and packaging label information for that system, and that all must 

be consistent with and not contravene the demonstration and notification to EPA. 

What commenters said: 

Chew commented that marketing materials used by the conversion manufacturer 

should provide very specific consumer information to prevent misapplication of the 

conversion system. Chew recommended that the materials list not only the test groups 

that may be retrofitted with a given system, but also spell out the test groups for which 

the system is not appropriate. 

Our response: 

EPA is finalizing the proposed marketing information requirements. EPA agrees 

that clear marketing material is important to minimize potential misapplication. While 

EPA does not believe it is practical to require manufacturers to list test groups to which 

the conversion system cannot be applied, marketing material must never imply, even 

tacitly, that a conversion system may be applied to any test groups other than those for 

which it was explicitly designed. 

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6.	 Small Volume Manufacturers and Small Volume Test Groups/Engine 

Families 

6.1	 Small Volume Status 

What we proposed: 

EPA proposed to allow eligible conversion manufacturers to use the existing 

regulatory procedures specific to light-duty and heavy-duty chassis certified vehicle small 

volume manufacturers and small volume test groups, set forth in 40 CFR 86.1838-01. A 

manufacturer is eligible for small volume manufacturer status for light-duty and heavyduty chassis certified vehicle procedures, if the manufacturer’s annual model year motor 

vehicle and engine total sales volume in all states and territories of the United States (or 

aggregate sales volume for manufacturers in an aggregate relationship) is less than 

15,000 units. A large volume manufacturer may also use small volume manufacturer 

certification procedures for test groups of vehicles which total less than 15,000 units. For 

small volume test group eligibility criteria for large volume manufacturers who 

participate in aggregate relationships, refer to 40 CFR 86.1838-01(b)(2) for more details. 

Heavy-duty engine small volume manufacturer status is tiered. Certain procedures 

apply to manufacturers with aggregate sales of less than 301 units, and other procedures 

may apply to manufacturers with aggregate sales volumes less than 10,000 units. Please 

refer to 40 CFR 86.098-14 and 40 CFR 86.096-24(e)(2) for details. 

What commenters said: 

Diesel 2 Gas commented that EPA should expand the definition of small volume 

manufacturer to include up to 50,000 units per year. 

ALTe commented that EPA should raise the cap to 25,000 units by the make and 

model of conversions. 

Chew commented that, for mixed-fuel and dual-fuel conversions EPA should only 

allow a statement of compliance in lieu of test data up to 5,000 annual sales per that 

specific system. 

Our response: 

EPA did not change the small volume manufacturer quantity thresholds in this 

rulemaking since this rulemaking relies largely on the already-established certification 

provisions, including the previously-established small volume manufacturer thresholds 

and provisions. Therefore, EPA is finalizing small volume status as proposed. 

33
 
 

 

 

 

 

 

 

6.2 Change in Small Volume Status 

What we proposed: 

EPA proposed that conversion manufacturers would be required to satisfy the 

requirements for large volume manufacturers or test groups/engine families if their 

annual sales volume surpasses the threshold for small volume manufacturer or test group 

status for a given model year. This requirement would apply even if the conversion 

manufacturer initially complied properly (in a previous model year) with the small 

volume requirements. Conversion manufacturers should be aware that this status change 

could result in new demonstration and notification requirements involving new testing 

under both the new and intermediate age programs. EPA proposed to require conversion 

manufacturers to report to EPA the number of conversion systems they have sold 

annually in an end-of-year submission. 

What commenters said: 

Chew commented that the proposed regulation does not provide compliance leadtime for a conversion manufacturer that has grown from a small volume manufacturer to 

a large volume manufacturer. 

Our response: 

EPA does not agree that a defined lead-time is necessary, since conversion 

manufacturers should be able to predict in advance and plan for changes in small volume 

status. 

6.3 Flexibilities for Small Volume Manufacturers and Small Volume Test 

Groups/Engine Families 

What we proposed: 

EPA proposed several flexibilities for small volume conversion manufacturers 

and test groups/engine families. The flexibilities fall into two categories: test 

group/engine family combinations and durability testing. 

For the new clean alternative fuel vehicle and engine conversion program, EPA 

proposed to allow small volume conversion manufacturers and small volume test 

groups/engine families to combine several OEM test groups/engine families into larger 

conversion test groups/engine families.

18 

EPA proposed to allow all small volume conversion manufacturers and small 

volume test groups/engine families to use assigned deterioration factors in lieu of 

durability testing. Additionally, EPA proposed that small volume conversion 

18 EPA also proposed broader groupings for intermediate age and outside useful life conversions. 

34
 
 

 

 

 

 

 

 

 

 

 

manufacturers and small volume test groups/engine families are eligible to use scaled 

deterioration factors for vehicles or engines that have accumulated more than 10,000 

miles. 

What commenters said: 

CSI and NatGasCar commented that the proposed requirements create an unlevel 

playing field for small volume manufacturers. CSI and NatGasCar commented that EPA 

should create a different testing process for small volume manufacturers that exempts 

them from confirmatory testing, allows them to use OEM deterioration factors, requires 

only one OBD test per manufacturer, allows carry forward sales exemptions to newer 

OEM model years if the manufacturer has been granted a certificate for a previous OEM 

model year, allows carry across of data to all engine tests groups for a year, make and 

model, and carry across of data for multiple OEMs. CSI and NatGasCar commented that 

certification procedures may be reasonable for OEMs, but it is financially burdensome 

for a small volume manufacturer to spend $100,000 minimum on a certificate to sell a 

small amount of conversions applicable to only one model year, make, and model 

vehicle. 

NTEA commented that the current regulatory structure effectively precludes 

many small businesses from participating in the alternative fuel conversion process. 

Our response: 

EPA is finalizing the small volume manufacturer and small volume test 

group/engine family requirements as proposed. EPA disagrees that it is appropriate to 

adopt additional flexibilities for small volume manufacturers such as those proposed by 

the commenters. EPA believes the new flexibilities being adopted under the revised fuel 

conversion regulations appropriately address small volume concerns. Many of the 

individual test procedures mentioned in the CSI and NatGasCar comments are discussed 

in section 7 “Demonstration Requirements.” 

The amended regulation codifies some important flexibilities for small volume 

conversion manufacturers and small volume test groups/engine families. The ability to 

combine test groups and engine families increases the number of vehicles and engines to 

which the cost for one set of test data applies. In addition this regulation continues to 

allow small volume conversion manufacturers and small volume test groups/engine 

families to use the same procedures available to small volume OEM manufacturers, 

including use of assigned deterioration factors, rather than requiring full durability 

testing. 

EPA acknowledges the CSI and NatGasCar comment about costs. EPA expects 

that this rule will result in cost savings for many converters. However, technology 

research and development costs will vary depending on conversion technology, fuel type, 

vehicle or engine age, applicability, and other factors. 

35
 
 

 

 

 

 

 

6.4	 Assigned Deterioration Factors (DFs) for Small Volume Manufacturers and 

Small Volume Test Groups/Engine Families 

What we proposed: 

EPA proposed to continue to allow small volume manufacturers or qualified small 

volume test groups/engine families to use assigned DFs in lieu of durability testing to 

predict emission rates at the end of a vehicle's or engine’s useful life. EPA also proposed 

to allow small volume conversion manufacturers to use scaled DFs if the test vehicle or 

engine has accrued more than 10,000 miles. 

What commenters said: 

NGVA commented that manufacturers employing EPA assigned DFs should also 

provide a statement confirming the durability of their systems and explain why they 

believe their system will not harm the emissions control system or degrade the 

environment. 

CSI and NatGasCar commented that small volume conversion manufacturers 

should be permitted to use the OEM DFs rather than the EPA assigned DFs. The 

comments state that the EPA DFs are too rigorous thereby making compliance with 

standards unnecessarily difficult. CSI and NatGasCar commented that the OEM DFs are 

appropriate because the OEM ran tests on the vehicle to generate the DFs. CSI and 

NatGasCar also commented that the current EPA assigned DFs are not representative of 

the current alternative fuel conversion technology. 

Our response: 

EPA agrees with NGVA’s comment. Assigned DFs, whether scaled or not, are 

intended to provide small volume manufacturers and small volume test groups/engine 

families with a streamlined pathway for demonstrating that their product is durable. 

However, conversion to a new fuel creates new challenges to assessing whether the 

engine and emission components will remain durable for the full useful life of the vehicle 

or engine. Therefore, EPA is finalizing a requirement that conversion manufacturers 

using EPA assigned DFs must submit supplemental information to confirm system 

durability and explain why the conversion technology will not cause emissions 

degradation in the converted vehicle/engine. 

EPA does not agree that the DFs OEMs generate for the initial test group or 

engine family certification are necessarily appropriate for the fuel conversion test group 

or engine family because the OEM DFs are calculated based on the original fuel and the 

original technology. EPA DFs are based on extensive analysis and a long-established 

policy for assigned DFs.

19 EPA continues to believe that EPA assigned DFs are 

appropriate for small volume manufacturers and small volume test groups/engine families 

19 http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=14285&flag=1. 

36
 
 

 

 

 

 

 

 

as an alternative to durability testing. A conversion manufacturer can always choose to 

run durability testing and generate new DFs, rather than using EPA assigned DFs. EPA 

periodically updates the assigned DFs using the data available through our OEM 

compliance program. 

7. Demonstration Requirements 

7.1 Comments Specific to Vehicle Demonstrations 

What we proposed: 

We proposed to base procedures for certifying new clean alternative fuel 

conversions, including confirmatory testing, on the certification procedures specified in 

40 CFR part 86, subpart A, B and/or S and 40 CFR part 1065, as applicable. For 

intermediate age vehicles, we proposed that conversion manufacturers would conduct the 

same exhaust and evaporative emissions testing as is required for certification to 

demonstrate that the converted vehicle or engine will continue to meet applicable 

standards. 

Please see ‘Comments on Age-Based Proposal’ below for discussion of outside 

useful life demonstration requirements. 

What commenters said: 

APG commented that EPA should outline critical concerns, operating conditions 

or thresholds for demonstrating that useful life standards can be met, but allow broader 

choices in the procedures to be used to demonstrate compliance. 

Reed commented that EPA’s demonstration requirement should require natural 

gas conversions to be subject to biannual SMOG tests. 

ALTe commented that the current federal test procedures may not be appropriate 

for plug-in hybrid-electric vehicles (PHEV) because the operating time of the internal 

combustion engine in the PHEV depends upon the design of the hybrid system and the 

specific EPA drive cycle. 

CSI, NatGasCar, and ALTe requested an exemption from confirmatory testing at 

EPA’s laboratory if the conversion manufacturer has conducted testing at an EPArecognized laboratory. 

Flex Fuel US requested clarification about whether a single confirmatory test 

from a fuel converter is sufficient if the converter uses the same engineering design of the 

fuel conversion system. 

Flex Fuel US commented that EPA should not require confirmatory testing at the 

EPA laboratory for fuel converted vehicles. 

37
 
 

 

 

 

 

 

 

 

 

 

Our response: 

EPA will continue to rely on existing test procedures in certification regulations 

and is not creating new test procedures to demonstrate compliance with CAA section 202 

standards in this rulemaking as suggested by APG. Should EPA in the future develop 

new OEM test procedures to demonstrate compliance with emissions standards, EPA 

would consider allowing conversion manufacturers to also use those procedures. 

EPA is not adopting a bi-annual smog-test as a compliance test because I/M-type 

testing is designed to different standards and different testing protocols than EPA 

certification emission standards. 

EPA is not adopting new drive cycles for PHEVs in this rulemaking, as suggested 

by ALTe, because this program relies largely upon existing regulatory test procedures 

that are already established for OEMs, including test procedures and other requirements 

for hybrid electric vehicles and PHEVs. 

EPA conducts confirmatory testing at its Ann Arbor, Michigan testing facility as a 

fundamental element of emissions compliance oversight. This process gives EPA 

confidence in the data submitted from OEM testing facilities, or from independent test 

labs which are typically used by fuel converters. EPA does not agree with comments 

from Flex Fuel US, CSI, NatGasCar, and ALTe suggesting that a single confirmatory test 

(or none at all) at EPA is sufficient if there is a similarity of design of a fuel converter’s 

technology, even as it is applied to many OEM test groups. The fuel conversion 

technology may be similar in design, but it is the interaction of the fuel conversion 

system with the OEM’s fuel control and emission control systems that will determine 

compliance with standards. EPA is retaining the option to confirmatory test fuel 

converted vehicles at its Ann Arbor testing facility. EPA continues to discover emission 

failures during confirmatory testing of both OEM vehicles and conversions. EPA believes 

confirmatory testing remains a critical component of the responsibility to apply due 

diligence in ensuring the environmental integrity of conversion systems. 

7.2 Comments Specific to Heavy-Duty Engine Demonstrations 

What we proposed: 

EPA proposed to require manufacturers of heavy-duty engine conversion systems 

to conduct all testing required for the originally certified engine, unless specifically 

excepted. 

What commenters said: 

EPA received many comments expressing concern about the expense and 

practical difficulties associated with FTP engine testing. Engine converters stated that the 

cost of removing an engine for testing and of conducting testing at a qualified laboratory 

can be prohibitive. 

38
 
 

 

 

 

 

 

 

 

APG commented that EPA should allow OEM vehicles that were originally 

engine certified to be chassis tested. APG further commented that EPA should allow 

chassis testing over a fixed road route or using a steady state test, using technology such 

as Portable Emissions Measurement Systems (PEMS), and that emissions testing should 

be conducted on the vehicle in its base level configuration, then on the converted fuel. 

Diesel 2 Gas commented that the proposed rule would require the removal of 

engines from heavy-duty vehicles to conduct a certification level emission data ‘engine’ 

demonstration. The comments stated that it is unnecessarily difficult and expensive to 

remove and reinstall entire engines when before and after testing on ‘complete vehicles’ 

would be adequate to demonstrate that emissions were not adversely affected by the 

conversion. Diesel 2 Gas further commented that the responsibility of the conversion 

manufacturers should be limited to demonstrating that the conversion does not cause the 

emission performance to deteriorate, particularly in cases where the conversion does not 

alter the original OEM configuration. The comments stated that PEMS testing is an 

appropriate demonstration method for intermediate age vehicles and engines because it 

provides demonstration data on a representative engine, avoids the logistical difficulties 

and excessive cost of removing engines for lab testing, is an accepted protocol for in-use 

compliance demonstrations, and is part of EPA’s in-use compliance demonstration for 

OEMs. 

Reed commented that EPA should allow PEMS testing and that emissions pretesting of vehicles is unnecessary. Reed also commented that EPA should follow the 

CARB 1994 Attachment A certification procedures for alternative fuel retrofit systems. 

Our response: 

EPA understands conversion manufacturers’ concerns about the expense of 

heavy-duty engine testing. However, the basis for exemption from the tampering 

prohibition under this program is the conversion manufacturer’s demonstration of 

compliance with applicable standards. At this time, there are no codified certification test 

procedures other than engine dynamometer testing through which manufacturers can 

demonstrate compliance with standards for vehicles greater than 14,000 pound gross 

vehicle weight rating (GVWR). Therefore EPA is finalizing as proposed the engine 

testing demonstration requirement for such conversions. 

As some commenters noted, EPA allows OEMs to use PEMS testing to satisfy 

certain compliance requirements. However, the use of PEMS is limited to screening inuse heavy-duty vehicles for excessively high emissions under field conditions. OEMs 

may not use PEMS testing results to certify engines. For these reasons, PEMS testing 

does not offer converters a viable alternative to engine dynamometer testing for purposes 

of demonstrating compliance with CAA section 202 heavy-duty engine standards. 

The procedures for using PEMS for field testing state, “These procedures are 

designed primarily for in-field measurements of engines that remain installed in vehicles 

39
 
 

 

 

 

 

 

 

 

 

 

or equipment in the field. Field-test procedures apply to your engines only as specified in 

the standard-setting part.”20 EPA currently allows PEMS testing to be used by OEMs to 

demonstrate compliance with in-use Not-to-Exceed (NTE) standards for on-highway 

heavy-duty diesel vehicles and engines. In-use NTE standards were promulgated by EPA 

to limit in-use emissions that might inappropriately exceed the applicable standards when 

engines were operated under conditions not found during traditional laboratory testing, 

sometimes referred to as “off-cycle emissions.”21 The final rule for in-use testing for 

heavy-duty diesel engines and vehicles states that the vehicle pass criteria used for the 

manufacturer-run, in-use NTE program does not correspond specifically to the criteria for 

showing compliance to the NTE standards, or that an engine family is in full compliance 

with the standards.22 As explained previously in this response to comments document and 

in the preamble, manufacturers of conversion systems for engines still within their useful 

life must demonstrate compliance with the CAA section 202 certification standards in 

order to qualify for an exemption from the prohibition on tampering. Therefore, 

converters seeking a tampering exemption must use the test procedure associated with 

those standards, which at this time is limited to the FTP testing on an engine 

dynamometer. Should EPA in the future adopt new test methods such as PEMS or new 

chassis cycles through which engine manufacturers can demonstrate compliance with 

CAA section 202 certification standards, EPA would consider making those new options 

available to converters. 

EPA is able to offer new flexibility to some conversion manufacturers working 

with engines for 8,500 to 14,000 pound GVWR vehicles. EPA considered and agrees 

with comments suggesting that manufacturers of clean alternative fuel conversion 

systems for heavy-duty engines for which a chassis certification option was available to 

the OEM should be permitted to use chassis certification test procedures, even if the 

OEM opted for engine certification. Thus EPA is finalizing an option for engine 

converters to meet vehicle rather than engine standards if chassis certification was 

available to the OEM. This option would apply only to those vehicles for which it was 

optional for the OEM to choose engine or chassis certification procedures. As such, this 

option will not apply to any engine for use in vehicles over 14,000 pounds GVWR or 

older than model year 2001 for Otto-cycle engines and model year 2007 for diesel 

engines. Conversion manufacturers choosing this option must designate test groups using 

the appropriate criteria as prescribed in this rule and meet all chassis-certification 

requirements set forth in 40 CFR part 86, subpart S.23 EPA is adopting this flexibility to 

remove an unnecessary economic barrier while maintaining necessary environmental 

protections. 

The Reed comment, suggesting that EPA allow use of 1994 CARB test 

procedures, refers to a CARB regulatory document describing the CARB approval 

20 40 CFR §1065.901(a).
 21 70 FR 34597 (June 14, 2005).
 22 Id. at 34603.
 23 These provisions (and available options) apply to 8,500 to 14,000 pound GVWR Otto-cycle complete 

and incomplete heavy-duty vehicles for model years 2001 and forward, and for 8500 to 14,000 pound 

GVWR compression ignition engines in complete and incomplete heavy-duty vehicles for model years
 

2007 and forward. See 40 CFR 86.1801-01, 86.1816-05, and 86.1863-07.
 

40
 
 

 

 

 

 

 

 

 

procedures for alternative fuel retrofit systems.24 CARB’s procedure compares baseline 

emission results from the pre- fuel converted engine to the post- fuel converted engine. 

The post- fuel converted results may not exceed the pre-fuel converted results by more 

than 10%. A deterioration factor is developed and applied to the post- fuel converted 

engine results. The deteriorated emission result, using a full useful life of 180,000 miles, 

may not exceed the baseline emission results by more than 30%. 

California’s compliance approach may or may not be able to correctly predict if a 

heavy-duty fuel converted vehicle still within its full useful life will meet the applicable 

EPA engine standards based on engine dynamometer testing. Meeting a CAA section 202 

standard, in this case engine based standards, is fundamental for all engines in the new or 

intermediate age programs in order to qualify for an exemption from tampering. We note 

that the CARB procedures referenced by Reed have subsequently removed any reference 

to the type of test procedure which must be used in the California program for heavy-duty 

vehicle fuel conversions. Based on our analysis of the referenced CARB document, EPA 

cannot consider this approach to adequately ensure compliance with EPA engine testing 

protocols and standards. 

7.3 Dual-Fuel and Mixed-Fuel Procedures 

What we proposed: 

EPA proposed to generally require mixed-fuel vehicles/engines to demonstrate 

compliance with applicable requirements for each fuel, which could entail testing on 

multiple fuel ratios to adequately represent worst case emission scenarios. 

What commenters said: 

The Collaborative commented that EPA should consider proposing ways to make 

it easier for mixed-fuel vehicles to be certified. The Collaborative comments focused on 

vehicles that burn diesel fuel and CNG simultaneously. The comments stated that the 

injection of CNG as well as diesel fuel into the engine significantly reduces CO2 

emissions and enables the remaining diesel fuel to burn more cleanly. The comments 

further stated that the percentage of CNG in the mix should be irrelevant as long as the 

resulting emissions from the fuel mixture are cleaner after the conversion. 

Diesel 2 Gas and APG commented that a simplified test procedure would be 

appropriate to demonstrate emissions compliance for their mixed-fuel systems, which are 

non-invasive and do not physically touch the engine or electronic controller, or bypass, 

defeat or alter any device or element of the engine system. 

24 Final Regulatory Order, Attachment A, Modifications to the “California Certification and Installation 

Procedures for Alternative Fuel Retrofit Systems for Motor Vehicles Certified for 1994 and Subsequent 

Model Years,” adopted by the CARB Board on July 27, 1995. 

41
 
 

 

 

 

 

 

 

 

 

 

Flex Fuel US commented that EPA should establish an E-85 test fuel specification 

that is representative of the American Society for Testing and Materials (ASTM) in-use 

standards and that EPA should not conduct cold start emission tests. 

Flex Fuel US requested that EPA allow the use of a Non-Methane Organic Gas 

(NMOG)/Non-Methane Hydrocarbon (NMHC) ratio to determine compliance with 

NMOG standards when vehicles are tested on E-85. This ratio could then be used to 

determine compliance in lieu of measuring NMOG using CARB procedures. 

Flex Fuel US commented that E-85 vehicles should only be confirmatory tested at 

a single ethanol/gasoline volumetric ratio. 

Flex Fuel US commented that EPA should consistently apply CARB’s NMOG 

test procedures or correct any inconsistencies or errors in the procedures. 

Our response: 

EPA is finalizing requirements for manufacturers of mixed-fuel vehicle/engine 

conversion systems to demonstrate compliance for each fuel, as proposed. EPA 

requested comment on alternative approaches but did not receive any data or information 

to support other test procedures that could be used to demonstrate mixed-fuel 

vehicle/engine compliance with EPA certification standards. 

As stated in the proposal, we understand that it may be appropriate to apply 

special testing considerations when evaluating new types of technologies such as those 

described by commenters. Converters may approach EPA to discuss special testing 

needs including development of worst case scenarios for “mixed-fuel” vehicle/engine 

testing. 

Ethanol fueled vehicles are subject to CARB NMOG measurement procedures 

because there is no accurate way at present to demonstrate compliance by simply 

measuring NMHC and multiplying by a manufacturer specific or industry-wide NMOG 

to NMHC ratio. 

EPA regulations for ethanol flexible fuel vehicles, a type of mixed fuel vehicle, 

require the EDV to be able to meet emission standards on any blend of ethanol and 

gasoline. However it presents an impractical testing burden to have manufacturers and 

fuel converters demonstrate compliance on more than two common test fuel types – those 

being gasoline and E-85. EPA has no plans for requiring flexible fuel vehicles to 

demonstrate compliance on more than these two fuels, even though EPA regulations give 

EPA authority to conduct confirmatory testing on other fuel blends. 

EPA understands the Flex Fuel US comment that E-85 test fuel specifications are 

needed and that test fuels and summer time in-use E-85 fuels should be similar in their 

physical and chemical properties. EPA may address this issue in a separate rulemaking, 

but it is beyond the scope of this final rule. 

42
 
 

 

 

 

Compliance with exhaust emission standards is almost always determined based 

on the successful control of the “cold start” emissions measured on the first phase of the 

FTP. EPA cannot eliminate cold start testing for ethanol flexible fuel vehicles. 

EPA is working to address inconsistencies in the CARB NMOG test procedures, 

but CARB is responsible for making revisions to its procedures. 

7.4 Good Engineering Judgment 

What we proposed: 

EPA proposed that all conversions must be designed and installed in accordance 

with good engineering judgment. The proposal provided numerous examples of good 

engineering judgment and described how EPA would assess a manufacturer’s technical 

approach in evaluating good engineering judgment. One example stated that OEM 

engines that use direct injection should employ alternative fuel technologies that also use 

direct fuel injection. 

What commenters said: 

APG commented that one-to-one equivalence in fueling technology is 

unnecessarily restrictive. APG further commented that their fuel mixer system for adding 

CNG to the diesel intake system is digitally controlled to only flow during appropriate 

conditions, and therefore it is impractical and unnecessary to install a set of high-pressure 

natural gas injectors and fuel rail(s) when their digitally controlled mixer can achieve 

good fuel control and low emissions. APG requested that the outside useful life 

demonstration requirement be rewritten to allow for their type of mixed-fuel delivery 

systems. 

Chew commented that the issue of “good engineering judgment” can be very 

subjective and a challenge without the full cooperation by the OEM. 

Flex Fuel US requested that “good engineering judgment” be extended to accept a 

statement of compliance in lieu of testing for OBD, canister loading and evaporative 

emissions testing if previous testing demonstrated compliance. 

Reed commented that outside useful life conversions should not be required to use 

“similar technology level” as the OEM motor, such as fuel injection needing to be done 

on fuel injection OEM motors. The comments stated that such a requirement ignores the 

fact that many alternative fuels are not in the same form as gasoline or diesel, and this 

technology matching does not determine solid engineering. 

Our response: 

43
 
 

 

 

 

 

 

 

 

EPA agrees with APG comments that engineering designs that differ from the 

OEM technology may still be capable of achieving good fuel control and low emissions. 

The examples of good engineering judgment that EPA provided in the proposal were not 

intended to be comprehensive or mandatory. Rather, the examples of good engineering 

judgment, including the fuel control example, represent EPA’s interest in seeing that the 

technical approach behind the conversion is of at least equivalent technical sophistication 

to the OEM design. 

While good engineering judgment may include some exercise of discretion, the 

documentation submitted to the EPA should include engineering analysis containing 

objective information and data supporting the declaration. For new and intermediate age 

vehicles/engines, the good engineering judgment documentation will include results of 

emissions tests conducted over FTP cycles at a qualified laboratory. FTP test results may 

also be submitted to help satisfy the outside useful life demonstration requirement. A 

clean alternative fuel conversion manufacturer is eligible for an exemption from the CAA 

tampering prohibition only if the conversion system is designed, constructed, and applied 

using good engineering judgment in addition to the other requirements of the rule 

including those applicable to the appropriate age-based categories. 

8. Durability Testing 

What we proposed: 

EPA proposed that for new and intermediate age vehicles and engines, conversion 

manufacturers would be required to conduct all applicable durability testing unless the 

conversion manufacturer is eligible for small volume manufacturer or small volume test 

group/engine family status permitting the use of assigned deterioration factors in lieu of 

durability testing. Large volume manufacturers would still need to conduct durability 

demonstrations following the requirements in 40 CFR part 86 regulations. 

What commenters said: 

Wallace commented that durability procedures are too complicated and without 

any real world practicality. Wallace suggested that EPA could instead rely on data from 

I/M programs to find problems with fuel conversion systems. 

Chew commented that EPA should test vehicles two or three years after 

conversion to verify their in-use emission levels. 

NGVA commented that the good engineering judgment demonstration should 

include evidence that a system will continue to maintain appropriate emissions and 

fueling control performance over its life. 

RRCT commented on durability concerns by suggesting EPA include provisions 

to ensure that alternative fuel types are suitable for the engine(s) in the conversion test 

44
 
 

 

 

 

 

 

 

group or engine family. The concern is that some engines being converted to alternative 

fuels may need to replace valves and valve seats with hardened components. 

Our response: 

EPA is finalizing the durability procedures as proposed. EPA disagrees with the 

Wallace comments stating that the durability procedures are too complicated and 

impractical. EPA believes that a durability demonstration or use of an assigned 

deterioration factor with accompanying supplemental information is essential to ensure 

that converted vehicles/engines remain as clean as the OEM configuration being 

replaced, for their full useful life. EPA also disagrees that I/M testing is suitable for 

ensuring that fuel conversions meet standards. Durability testing is conducted prior to a 

manufacturer’s demonstration, not after a vehicle/engine is in customer care. Therefore 

I/M in-use tests are not an appropriate substitute for durability testing. In addition, I/M 

tests are designed to find gross emitters and vehicles with OBD trouble codes and an 

illuminated MIL. I/M testing uses much different and less accurate equipment and test 

procedures relative to 40 CFR part 86 and is therefore incapable of making an accurate 

pass/fail determination for compliance with 40 CFR part 86 standards. 

EPA does not agree with the Chew comment that EPA should regularly test 

converted vehicles/engines to assess system durability. EPA retains authority to conduct 

such testing, and intends to use testing along with other compliance tools to monitor 

emissions performance of converted vehicles/engines in customer service. 

EPA believes that the durability concerns raised by NGVA and RRCT will be 

addressed by the requirement for large volume converters to conduct durability 

demonstrations and small volume manufacturers and small volume test groups/engine 

families to provide technical information to supplement use of an assigned deterioration 

factors. The supplemental statement must describe and demonstrate the compatibility of 

the vehicle/engine with the alternative fuel type. If the information EPA receives is 

inadequate, EPA will request additional information to provide confidence that the 

aftermarket fuel conversion system is clean and durable. In addition, sections 206, 207 

and 208 of the CAA authorize EPA to establish procedures to ensure that production 

vehicles and engines comply with emission standards when they are new and continue to 

comply with emission requirements after they are in customer service. EPA intends to 

test vehicles and engines in all age-based categories. 

9. Year End Reporting 

What we proposed: 

EPA proposed to require conversion manufacturers to report annually to EPA the 

number of conversion systems they have sold in an end-of year submission. 

45
 
 

 

 

 

 

What commenters said: 

NGVA commented that EPA should require a summary report of total sales by 

alternative fuel type and possibly vehicle types (i.e., compact, passenger car, light-duty 

truck, etc.) should be provided to help industry better assess market growth and impact of 

aftermarket conversions. 

Our response: 

EPA agrees with the comment and is finalizing a requirement that the end-of year 

summary report should include total sales by alternative fuel type and vehicle/engine 

types. 

10. Technical Amendments 

What we proposed: 

We proposed several technical amendments to 40 CFR part 86, subpart S which 

are applicable to the exhaust and evaporative emission testing requirements for both 

OEM and converted vehicles using gaseous alternative fuels. The purpose of these 

amendments is to allow flexibility in determining compliance with EPA NMOG 

standards for vehicles, and also to allow statements of compliance in lieu of test data for 

meeting exhaust emission standards for formaldehyde (HCHO), and evaporative 

emissions. For purposes of this regulation, CNG, LNG, liquefied petroleum gas (LPG), 

and hydrogen fuels are eligible for the technical amendments described below. 

We specifically sought comment on whether there are other test procedures in 40 

CFR part 86 or part 1065 which should be updated to address concerns specific to certain 

alternative fuels. 

What commenters said: 

NPGA commented that they support the various technical amendments proposed 

by EPA. 

Our response: 

EPA will finalize the technical amendments as proposed. 

46
 
 

 

 

 

 

11. Comments on Age-based Proposal 

11.1 General Comments on age-based proposal 

What we proposed: 

EPA proposed to establish demonstration and notification protocols that would be 

based on the age of the vehicle or engine being converted: (1) “new and relatively-new” 

(referred to as “new” in the preamble and regulations), (2) no longer new but that still fall 

within EPA's definition of full useful life, “intermediate age vehicles,” and (3) outside 

EPA’s definition of useful life. The proposed demonstration for new vehicles/engines 

was certification, much like previous practices. The proposed demonstration for 

intermediate-age vehicles/engines was compliance with applicable standards. EPA 

proposed and sought comment on three options for the outside useful life demonstration 

(see specific age-based discussions, below). 

What commenters said: 

EPA received numerous comments in support of the age-based proposal. Several 

commenters offered suggestions for modifications to specific elements of the programs. 

APG comments supported the proposal to use a publicly available list to identify 

intermediate age and outside useful life conversion systems that have satisfied the 

demonstration and notification requirements. 

The Auto Alliance commented that EPA should not change the options for 

conversion manufacturers to gain an exemption from the tampering prohibition and 

should apply the current certification requirement for all age categories. 

Reed commented that the age-based categorization is not applicable to heavy-duty 

engines and should be abandoned. 

NTEA commented that, while it is important that EPA ensure compliance of a 

vehicle throughout its useful life, it must balance the regulatory environment so that even 

cleaner conversions, especially of older vehicles, are not only possible but attractive. 

NTEA also stated that providing converters of older vehicles the option of submitting 

documentation of good engineering judgment or test data may strike such a balance. 

Our response: 

We disagree with the Auto Alliance comment that EPA should make no changes 

to the current options available to fuel converters to gain an exemption from the 

tampering prohibition. EPA undertook this rulemaking with the intent of providing 

compliance flexibilities appropriate for the conversions industry while maintaining 

appropriate environmental oversight. The Auto Alliance did not present evidence to 

support a conclusion that an across-the-board certification demonstration requirement is 

47
 
 

 

 

 

 

 

necessary. EPA is finalizing an age-based program, as proposed. EPA believes an agebased program achieves a proper balance of requiring data and documentation to be 

presented to EPA to ensure that fuel converted vehicles and engines satisfy CAA 

conditions for exemption from the tampering prohibition. 

EPA disagrees with Reed’s comment that the age-based proposals are not 

applicable for heavy-duty engines. EPA understands that heavy-duty engines are 

frequently rebuilt and therefore are in-service well beyond their regulatory full useful life. 

The prohibitions against tampering do not expire at the end of the regulatory full useful 

life period, and therefore the policies in this final regulation for this category of fuel 

converted engines are necessary to provide a clear pathway for obtaining an exemption 

from tampering. 

11.2 New (Certification) 

What we proposed: 

EPA proposed to largely retain current certification requirements for 

manufacturers of conversion systems for new vehicles and engines, while providing some 

new flexibility in grouping such vehicles for certification purposes. The proposal defined 

“new and relatively-new” vehicle or engine clean alternative fuel conversions as those for 

which the date of conversion is in a calendar year that is not more than one year after the 

original model year of the vehicle or engine. We requested comment regarding whether 

EPA properly identified the vehicle and engine age range for which certification is 

appropriate and should be required for conversions. We further requested emissions or 

other data to support comments suggesting a different age range than the proposed two 

year period. 

What commenters said: 

NGVA commented that the current proposal to define new vehicles as those that 

are less than two years old is unnecessarily restrictive. NGVA further stated that the 

definition of “new” vehicle should be scaled back to cover vehicles from the current 

model year and vehicles or engines that are one year old or less. 

Our response: 

EPA is finalizing the “new” age category definition and compliance requirements 

as proposed. When developing the proposed and final rules, EPA considered many 

options with respect to how many years should fall into the new vehicle/engine category. 

EPA seeks to maintain a level playing field between OEMs and converters to avoid any 

perceived incentive that might otherwise exist for OEMs to convert a certified traditional 

configuration rather than to certify an alternative fuel configuration in the first place. A 

certificate of conformity is also appropriate because vehicles/engines in the new category 

were entered into commerce as the subject of a recently issued OEM certificate of 

conformity and such vehicles/engines typically have the majority of their useful life 

48
 
 

 

 

 

 

 

 

 

 

remaining. In addition, most vehicles and engines that received conversion certificates 

under previous regulations were less than two years old. 

EPA considered many options for the age threshold between the new and 

intermediate age programs. The decision to finalize a threshold of about two years 

reflects several factors. These include the interest described previously in maintaining 

consistency with OEM requirements; the need for an OEM-like demonstration when 

converting vehicles and engines that still resemble the technical condition of the original 

product; and the fact that most conversions under the previous subpart F regulations took 

place within the first two years of a vehicle’s or engine’s regulatory useful life. We chose 

two years as the cut-off point for the new program to cover the vehicles and engines 

which are most likely to be converted, and which, because most of their useful life still 

remains, should be subject to the most rigorous demonstration requirement. No 

commenters provided data or technical justification to support a different age threshold 

than the one EPA proposed. Absent substantive evidence to support a different approach, 

EPA is finalizing the certification age threshold in the definition of “new and relativelynew,” as proposed. 

11.3 Intermediate Age 

What we proposed: 

We proposed that converters of intermediate age vehicles and engines could 

qualify for an exemption from the tampering prohibition by obtaining a certificate of 

conformity, or by demonstrating through testing that the converted vehicle or engine will 

continue to meet applicable standards through its useful life. Intermediate age was 

defined in the proposal as being more than one year after the original model year of the 

vehicle or engine, but still within useful life. 

The proposed program for intermediate age vehicles and engines maintained 

many of the existing certification test procedures, but departed from the existing subpart 

F requirements in several notable areas. The demonstration of compliance with applicable 

standards would use the same procedures required of certified conversion manufacturers 

for exhaust and evaporative emissions testing. However, instead of conducting OBD 

demonstration testing as required for certification, intermediate age converters would 

attest that the OBD system is fully functional. The notification process would also be 

significantly different for intermediate age vehicles and engines. Conversion 

manufacturers would still submit test data, attestations, and other required information to 

EPA; however the notification process would be streamlined. 

What commenters said: 

The Auto Alliance commented that certification should be required for all age 

categories and that there is no need for an intermediate age program. 

49
 
 

 

 

 

 

 

 

 

 

 

 

 

 

Reed commented that the proposal is not clear if emissions testing required for 

intermediate age vehicles applies to each conversion or if the testing can be done on a 

representative vehicle. 

RRTC commented that vehicle and engine fuel conversion systems certified under 

the new vehicle program should immediately qualify to be listed under EPA’s 

intermediate age program without generating new OBD demonstration data or paying 

certification fees. RRTC also commented that EPA could eliminate the intermediate age 

category and make certification permanent, or transfer certified vehicles and engines into 

the intermediate age program after they are one year old instead of two. 

Roush supported the proposed intermediate age program but recommended a 

different evaporative emissions demonstration for bi- or dual-fuel conversions, and 

outlined details for EPA to consider adding to both intermediate age and outside useful 

life demonstrations. Roush suggested requiring a detailed description of component parts 

and one or more FTP tests to demonstrate proper canister purge. The components 

description would include information such as materials specifications and permeation 

rates to show that the converter used good engineering judgment in designing the 

evaporative emissions system. 

CSI commented that the intermediate age and outside useful life programs should 

only be open to companies that have already obtained a certificate or otherwise worked in 

calibration. Otherwise, companies who have never certified with EPA would be allowed 

into the market, penalizing those who have invested extensive time and money following 

EPA’s past provisions. 

Flex Fuel US commented that fuel converters should first certify under EPA’s 

new vehicle program before being allowed participate in the intermediate or outside 

useful life programs. 

Wallace commented that he supported the public hearing testimony of IMPCO 

that a shorter intermediate age range would be better for alternative fuel fleet growth. 

AAF commented that they do not support the inclusion of the proposed 

intermediate age life category and it must be removed from changes to the regulations. 

AAF stated that removing the current EPA requirement that a system undergo testing to 

ensure that it meets minimum standards and works with the OEM OBDII system would 

allow uncertified and untested systems into the marketplace with no control. 

Our response: 

EPA is finalizing the intermediate age requirements largely as proposed. EPA 

disagrees with the Auto Alliance and AAF that all vehicles and engines must be certified 

to gain exemption from the tampering prohibition. EPA believes the flexibilities that 

characterize the intermediate age program offer the right balance between assurance of 

environmental compliance and testing burden. EPA believes that a reduced OBD 

50
 
 

 

 

 

 

 

demonstration requirement is appropriate for intermediate age conversions. See section 

5.6 for more details about the intermediate age OBD demonstration. 

The preamble and regulations describe in detail evaporative emissions statements 

of compliance and attestation that converters must submit in their notification to EPA for 

intermediate age vehicle and engine conversions. The conversion manufacturer must 

have sufficient basis to prove the statements are valid. The Roush comments suggesting 

FTP testing to demonstrate canister purge offer an example of one way a converter might 

support the canister purge statement of attestation set forth in 40 CFR 

85.515(b)(10)(iii)(D) and 85.520(b)(6)(iii)(D). Similarly, the components description 

Roush suggested might be used to support the statement of compliance for vehicles 

operated on CNG, LNG, LPG, or hydrogen fuels found in 40 CFR 86.1829-01(b)(2)(i). 

In response to Reed’s comment, the regulations require testing to be conducted 

on a worst case test EDV for both new and intermediate age programs. See section 5.4 for 

further discussion. 

EPA does not think it is necessary to limit entry into the intermediate age or 

outside useful life program to those conversion manufacturers who have previously 

certified. The demonstration requirement for exemption from tampering under the 

intermediate age program is submission of emissions data that show that the converted 

vehicle/engine meets applicable emission standards. The demonstration requirement for 

exemption from tampering under the outside useful life program is submission of 

technical information that shows that emissions from the converted vehicle/engine will 

maintain or improve upon emissions from the OEM vehicle/engine being converted. EPA 

believes these demonstrations are sufficiently protective for intermediate age and outside 

useful life conversions to qualify for exemption from the tampering prohibition. 

11.4 Outside Useful Life 

What we proposed: 

The proposal offered for comment three approaches through which manufacturers 

of clean alternative fuel conversion systems for outside useful life vehicles and engines 

might qualify for an exemption from the tampering prohibition. The proposal stated that 

EPA would finalize only one of the options. 

Option 1 would require manufacturers of conversion systems for outside useful 

life vehicles and engines to satisfy the demonstration requirement by submitting to EPA a 

detailed description of the conversion system. The submission would need to provide a 

level of technical detail sufficient for EPA to confirm the conversion system’s ability to 

sustain acceptable emission levels in the intended vehicle or engine. 

Option 2 would require manufacturers to satisfy the demonstration requirement by 

submitting FTP data showing that the converted vehicle/engine meets the useful life 

51
 
 

 

 

 

 

 

 

 

 

 

 

standard, or data from back-to-back tests showing that emissions do not increase after 

conversion. 

Option 3 would require manufacturers to submit a technical description as in 

Option 1, along with a demonstration that the OBD system is functioning properly. The 

OBD demonstration would involve using an OBD scan tool and submitting the report to 

EPA. 

We proposed that, while the demonstration requirement would differ among the 

three options, all other elements of the outside useful life program would be the same, 

including the notification process and the public listing of conversion systems qualifying 

for EPA-compliant status. We also proposed that the same requirements and criteria for 

test groups, engine families, and evaporative refueling family designations for 

intermediate age vehicles and engine would also apply to outside useful life vehicles and 

engines. 

We requested comment on all aspects of the outside useful life demonstration 

options and especially on the relative advantages and disadvantages of each of the 

options with regard to clarity of what would be required, ability of conversion 

manufacturers to satisfy the demonstration requirement, quality of information EPA 

would receive to evaluate emissions performance and durability, and enforceability. 

What commenters said: 

General Comments: 

Roush commented that the outside useful life exhaust demonstration should entail 

a comparison of FTP data from testing the vehicle on the original fuel and the converted 

fuel. Roush further commented that EPA should streamline the evaporative 

demonstration process relative to certification, and provided specific suggestions for how 

to do that. Their suggestions included EPA approval by design and approval based on 

data demonstrating that canister purge function is identical when operating on the fuel 

used by the OEM at the time of the original certification, and when the vehicle is 

operated on the alternative fuel. 

RRCT commented that they did not support any of the outside useful life options 

because all three had limitations. They further commented that EPA should not allow 

untested aftermarket systems be installed on outside useful life vehicles. 

Reed commented that their experience in the other countries has shown that a lack 

of emission testing requirements has resulted in inferior CNG conversion products being 

sold and has therefore slowed the adoption of CNG engine technology. 

Caterpillar commented that they agree with EPA’s proposal to use the same test 

procedures as the intermediate age program for the outside useful life compliance 

demonstration. 

52
 
 

 

 

 

 

 

 

Wallace questioned whether EPA would ever use data submitted under Option 2 

or Option 3 as the basis for an enforcement action. 

Comments on Option 1: 

APG comments generally supported the Option 1 technical description 

demonstration requirement and stated that it is appropriate to include emissions data in 

the submission. 

Diesel 2 Gas commented that they believe Option 1 is appropriate for outside 

useful life vehicles. 

Wallace commented the he supports Option 1 and that EPA should rely on 

existing periodic state emissions testing. 

Florida DEP commented that they support Option 1 and agree that it is 

appropriate to require manufacturers to submit a sufficiently detailed description to show 

that the conversion technology is technically sound and is applied according to principles 

of good engineering judgment. 

Comments on Option 2: 

APG commented that they agree with the proposed requirements to submit two 

sets of exhaust emission test data, with the first conducted before conversion and the 

second submitted after conversion under Option 2. However APG also commented that 

EPA should offer less burdensome alternatives to engine-dynamometer testing. 

CVEF commented in support of Option 2 with modifications. The comments 

stated that OBD scan tool procedures are not adequate and that EPA should require full 

OBD system testing in addition to an engineering judgment statement. 

TCEQ commented in support of Option 2. 

NGVA supported both options 2 and 3. NGVA stated that the final rule could 

allow two separate pathways for beyond useful life vehicles and engines even though 

EPA indicated that only one option would be finalized. NGVA also commented that it is 

not appropriate to select only one option if other options truly have merit and that 

therefore both options 2 and 3 should be retained in the final rule. 

Reed commented that “pre-testing,” meaning conducting a baseline emission test 

before an outside useful life vehicle is fuel converted, is unnecessary and even improper. 

Reed expressed concern that the baseline test may be conducted on an unrepresentative 

vehicle, thereby making the results obtained on the fuel converted vehicle questionable. 

Reed stated that such comparisons could result in an EPA approval that results in 

53
 
 

 

 

 

 

 

 

building poorly designed conversion systems for vehicles/engines in the outside useful 

life program. 

Comments on Option 3: 

Utah commented in support of Option 3 as it would provide states and EPA with 

the highest assurance that the OBD system is intact. Utah further suggested allowing 

Option 1 for vehicles that do not have an OBD system. 

NGVA commented that EPA should adopt both Options 2 and 3 since both 

options have merit. 

Chew commented that he supports Option 3 because it includes the submission of 

demonstration data as well as validation that the OBD system is functioning properly. 

Chew also stated that under most state I/M programs, each OBD test costs only about 

$30. 

Our response: 

EPA is finalizing the outside useful life demonstration described in the proposal 

as Option 3. EPA believes that the combination of a detailed technical description and an 

OBD scan tool test report will provide sufficient information to determine whether a 

conversion system merits exemption from the tampering prohibition by maintaining or 

improving upon emissions from the original configuration vehicle or engine. EPA further 

believes that the burden associated with satisfying this demonstration requirement is 

reasonable for outside useful life converters. 

EPA received comments in support of all the outside useful life options presented 

in the proposal. However, the comments favoring Option 2 did not provide data or other 

substantive evidence to support a conclusion that the additional cost and burden 

associated with two sets of FTP tests would be justified for outside useful life vehicles 

and engines. EPA believes that the good engineering judgment demonstration 

requirement will provide a sufficient basis for assessing the technical viability of 

conversion systems intended for outside useful life vehicles and engines. In addition, the 

OBD scan tool procedure will demonstrate that the OBD system is functional after 

conversion. 

EPA thoroughly evaluated all three options for the outside useful life 

demonstration requirement. Ultimately the decision to finalize Option 3 resulted from 

balancing concerns about a sufficiently robust environmental demonstration with careful 

consideration of the cost concerns of the conversion industry about Option 2, particularly 

for situations in which back-to-back FTP testing would be necessary. EPA recognizes 

that the cost and practical burden of back-to-back FTP testing could inadvertently limit 

participation of converters with well-engineered and potentially environmentally 

beneficial conversions from the outside useful life program. 

54
 
 

 

 

 

 

 

Options 1 and 3 include technically rigorous but potentially less costly 

demonstration requirements. EPA estimated the cost for most converters to complete an 

Option 1 or Option 3 demonstration would be far less than Option 2, since Option 2 could 

require two sets of tests. The only difference between Options 1 and 3 is the addition in 

Option 3 of an OBD scan tool report to the good engineering judgment demonstration. 

EPA is finalizing Option 3 over Option 1 because, for very little additional cost, it 

provides a strong measure of assurance that the OBD system functions properly and that 

emissions from the converted vehicle/engine do not exceed OBD thresholds. 

The Option 3 good engineering judgment demonstration can include test data. 

Thus EPA may request that the manufacturer submit emissions results from back-to-back 

FTP testing if EPA believes such data is necessary to fully evaluate a system’s viability. 

Similarly, converters may voluntarily use test procedures outlined in Option 2 to support 

their good engineering judgment demonstration. 

The Roush proposals for alternative paths for dual-fuel conversions to 

demonstrate outside useful life compliance with exhaust and evaporative emission are 

similar to the proposed Option 2. As described above, EPA believes that the good 

engineering judgment demonstration requirement, which could include testing, in 

combination with the OBD scan tool report, will provide a sufficient basis for assessing 

the technical viability and emission control system integrity of conversion systems 

intended for older vehicles/engines. Converters may submit results from FTP testing on 

the original fuel and FTP testing on the new alternative fuel to support their good 

engineering judgment demonstration in conjunction with data showing that the 

evaporative emission system purges hydrocarbon in an identical manner when operating 

on the OEM base fuel and on the alternative fuel. Please see section 11.3 for a response 

to Roush’s comments about an evaporative emission demonstration for dual-fuel and 

mixed-fuel vehicles. 

EPA disagrees with Reed’s comment that before and after testing is inappropriate 

for vehicles/engines in the outside useful life program. Outside useful life converters 

must submit a detailed technical description of the conversion system, including emission 

test data if requested, to allow EPA to evaluate the emission performance and durability 

of the conversion system. If this information is satisfactory, including a satisfactory OBD 

scan tool report if the vehicle/engine is OBD equipped, EPA is confident that the 

conversion system in question meets the criteria for an exemption from tampering. 

Reed’s concern that a baseline test could be conducted on an unrepresentative vehicle, 

thereby making the results obtained on the fuel converted vehicle questionable is 

addressed in the requirement that the EDV/EDE must be a worst case vehicle/engine that 

adequately represents the test group/engine family. An unrepresentative vehicle does not 

satisfy the good engineering judgment criteria for a qualified worst case EDV/EDE. 

In response to Caterpillar’s support for applying the intermediate age program to 

outside useful life vehicles/engines, EPA will consider an intermediate age demonstration 

as an acceptable demonstration of outside useful life compliance. However, since the full 

useful life standards are no longer applicable to vehicles/engines outside useful life, EPA 

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does not agree that this is the only pathway for conversion of vehicles and engines 

outside useful life. Therefore EPA is finalizing both the ability to use the intermediate 

age program as well as the outside useful life program called Option 3 in the proposal. 

EPA fully intends to use the information provided in conversion manufacturer 

demonstration and notification submissions to fulfill its compliance oversight 

responsibilities, including undertaking enforcement action when necessary. 

11.5 Outside Useful Life Subcategories 

What we proposed: 

We requested comment on whether to establish a subcategory of outside useful 

life vehicles and engines that reach the mileage threshold for outside useful life status 

before they reach the age threshold in years. EPA also requested comment as to whether 

manufacturers of conversion systems for this subcategory of vehicles and engines should 

be required to satisfy a different demonstration requirement than would be required for 

conversion of vehicles/engines in the “old by year” outside useful life subcategory. 

What commenters said: 

TCEQ recommended that the criteria for categorizing the outside useful life 

program be based solely on vehicle age without consideration for mileage accumulation, 

thereby negating the need to establish a subcategory of ‘younger’ outside useful life 

vehicles that may have exceeded their useful in mileage, but not in age. 

Wallace commented that EPA should not make two outside useful life 

subcategories. He commented that we should expect consumers to be able to understand 

the years or mileage threshold concept. 

Caterpillar commented that the category of engines/vehicles outside the emissions 

useful life should be based on the established definitions of either mileage or years, 

whichever occurs first, rather than be based on only years. 

NGVA commented that they have not developed a position on whether vehicles 

or engines that are outside of their useful life only because of mileage should only have 

the option of pursuing Option 2. 

APG commented that EPA should define outside useful life associated with 

vehicle mileage or operational time rather than age in years because engine wear is a 

direct function of usage and maintenance. APG also stated that exhaust system 

aftertreatment degradation occurs during engine/vehicle operation, and age (without 

operation) in a properly maintained engine and vehicle does little to degrade the engine 

function. 

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Our response: 

EPA is finalizing a single outside useful life category that maintains the age-ormileage threshold, whichever comes first. EPA agrees with the Caterpillar and Wallace 

comments stating that the statutory definition of useful life, which is reached by either 

age or mileage (or hours, if applicable), is the appropriate threshold for the outside useful 

life clean alternative fuel conversion program. Creating a separate subcategory of outside 

useful life vehicles would create unnecessary confusion and would not provide an 

environmental benefit. EPA disagrees with TCEQ’s comment that the criteria for the 

outside useful life program should be based solely on vehicle age. EPA’s emissions 

durability program is based on years of experience using accelerated aging cycles, such 

as rapid mileage accumulation on test tracks or bench aging of emission control 

components on a laboratory engine dynamometer. EPA believes the durability of key 

emission control components such as the catalyst is generally a function of the quantity of 

exhaust gas which passes through it, not simply the age of the catalyst. Therefore, EPA 

believes that vehicle mileage/engine hours of use are at least as important if not more 

significant in predicting emission system deterioration than vehicle/engine age in years. 

12. Other Comments Related to this Rulemaking 

12.1 Averaging, Banking, and Trading (ABT) 

What we proposed: 

We did not propose any ABT provisions for clean alternative fuel conversions. 

What commenters said: 

Caterpillar commented that fuel converters should be permitted to use ABT 

provisions. 

Our response: 

ABT provisions are appropriate for the original equipment vehicle or engine 

certificate holder. However, ABT programs, like fleet average standards, are not 

generally appropriate for clean alternative fuel conversion manufacturers because the 

fleet of vehicles/engines to which a conversion system may be applied has already been 

accounted for under the OEM’s ABT program and fleet average. An OEM creditgenerating vehicle that is subsequently fuel converted would create duplicative credits if 

fuel converters were to participate in ABT programs. The OEM fleet average is generally 

derived from the production- or sales-weighted average of individual test group/engine 

family certification levels in a given model year. Under the clean alternative fuel 

conversion program, conversion manufacturers will comply with the certification 

standard applicable to OEM vehicles or engines, if the vehicle/engine is within its useful 

life, or will demonstrate that emissions are not degraded after conversion, if the converted 

vehicle/engine is outside useful life. Accordingly, clean alternative fuel conversions will 

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be consistent with the applicable OEM standard and will not affect the OEM fleet 

average. Therefore it is not necessary to require compliance with an additional clean 

alternative fuel conversion fleet average. There are no provisions allowing fuel converters 

to participate in ABT, and EPA is not making any changes with respect to ABT options 

at this time. 

12.2 California Regulations 

What we proposed: 

We proposed to streamline the compliance process for clean alternative fuel 

conversion manufacturers pursuant to our CAA authority. California maintains its own 

mobile source emissions program, which is implemented by CARB. EPA’s proposal did 

not address the CARB program for alternative fuel conversions. 

What commenters said: 

IMPCO stated that EPA should clarify that EPA approved retrofit systems may be 

used in states that have not specifically adopted CARB retrofit standards. The 

Collaborative and NGVA stated that EPA should provide guidance regarding the legality 

of converting vehicles in states that have adopted CARB regulations. 

Our response: 

EPA’s final rule does not address this issue. Questions regarding California’s 

retrofit regulations are beyond the scope of this rule. California’s regulations pertaining 

to alternative fuel conversions for light-duty vehicles are located in title 13 California 

Code of Regulations sections 2030 and 2031, and those for heavy-duty are located in 

section 1956.9. Manufacturers introducing conversion kits into commerce in California 

states that adopt California standards will need to address these requirements. Questions 

regarding California’s program should be directed to CARB. 

12.3 Associated Costs of this Rulemaking 

What we proposed: 

The proposal presented an estimate of costs associated with satisfying the 

proposed demonstration requirements for conversion manufacturers seeking an 

exemption from the tampering prohibition. 

What commenters said: 

Reed commented that there were basic flaws in EPA’s estimate of costs for 

heavy-duty engine conversions. Reed further commented that, while EPA in general 

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accurately estimated the cost of a single emissions test for a heavy-duty engine, new 

engines rarely pass on the first test and therefore EPA had underestimated the costs. 

IMPCO stated that conversion manufacturers must undergo rigorous, costly, and 

time-consuming certification testing and diagnostic validation that adds significant time 

and expense to the cost of every test group, usually for only a couple hundred units of 

sales per test group. IMPCO also commented that the proposed new label content would 

create a proliferation of labels and result in increased label printing costs that would recur 

each year when certificates are renewed. 

Our response: 

EPA’s cost analysis estimated the cost reduction resulting from the proposed 

regulatory changes. The estimate did not include the costs converters might incur for 

technology research and development because they are not expected to change as a result 

of this rulemaking. 

EPA does not agree with the comment suggesting that the new label content will 

create a proliferation of labels that conversion manufacturers need to print, thereby 

increasing costs. Each certificate or notification represents a unique combination of fuel 

conversion test group/engine family and evaporative/refueling family. A conversion test 

group/engine family may represent more than one OEM test group or 

evaporative/refueling family, and the label may contain all applicable OEM test groups 

and evaporative/refueling family combinations to which the conversion system is 

applicable. The revised label content must now list the OEM test group(s) for which the 

conversion system is appropriate. However, EPA expects that any potential costs 

associated with satisfying this requirement will be offset by other features of the new 

regulations. In particular, it will now be possible for conversion manufacturers to 

combine more OEM test groups under a single fuel conversion test group. EPA also notes 

that conversion manufacturers will no longer need to renew certificates annually to retain 

their tampering exemption, and will therefore not need to print new labels each year. 

12.4 Zero Emission Components 

What we proposed: 

We did not propose any provisions for zero emission components. 

What commenters said: 

ConVerdant commented that “zero emission” components that do not modify or 

adversely affect the engine and emission control system should be excluded from the 

proposed and existing sections of the part 85 conversions regulations. 

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Our response: 

EPA is finalizing coverage of all conversion components under 40 CFR part 85 as 

proposed because EPA believes it is important to provide a clear regulatory pathway for 

all converters seeking an exemption from the tampering prohibition. Even components 

that are assumed to have no emissions impact because they do not directly modify or 

affect the engine and emission control system may adversely affect exhaust and/or 

evaporative emissions. An example is the conversion of an OEM certified hybrid electric 

vehicle (HEV) to a plug-in hybrid electric vehicle (PHEV). The addition of PHEV 

technology to the OEM certified HEV may affect the number and frequency of “cold 

starts” over EPA defined test cycles. Effective exhaust emission control requires that the 

catalyst maintain a threshold operating temperature. An increase in “cold starts” over the 

test cycles may adversely affect exhaust emission compliance by reducing the catalyst 

operating temperature following a period of engine shutdown. Similarly, reducing the 

amount of the evaporative emission canister purge due to reduced engine operation may 

adversely affect compliance with evaporative emission standards. 

12.5 Engine versus Vehicle Certification 

What we proposed: 

EPA proposed that conversion manufacturers demonstrating compliance with 

applicable emission standards to qualify for a tampering exemption would do so 

according to the same standards and test procedures in place for the OEM. There are 

some differences in the way the vehicle and engine regulations apply. 

What commenters said: 

ALTe questioned whether certification is based on the engine or the underlying 

vehicle. 

Our response: 

EPA clarifies that our approach is a legacy approach; that is, a conversion 

manufacturer must demonstrate compliance using the same standards and test procedures 

in place for the OEM. 

12.6 Certificate Expiration 

What we proposed: 

We proposed that conversions of new vehicles and engines would need to be 

covered by a certificate of conformity to qualify for an exemption from the tampering 

prohibition. We also proposed to allow, but not require, conversions of intermediate age 

vehicles and engines to qualify for an exemption from the tampering prohibition by 

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obtaining a certificate of conformity. The proposal stated that a certificate is valid until 

December 31st of the model year on the certificate.25 

What commenters said: 

EPA received numerous comments regarding certificate eligibility and expiration. 

RRTC stated that EPA should issue certificates for intermediate age vehicle and 

engine conversions and that the certificates should not need to be renewed from year-toyear. 

NPGA commented that certificates issued under the “new” vehicle and engine 

framework should not expire and should require no renewal. NPGA stated that nonexpiring certificates would effectively eliminate the need for an intermediate age 

grouping and avoid potential funding problems that could arise for kit manufacturers who 

apply for grants from the Department of Energy that are dependent upon EPA 

certification. 

IMPCO commented that certificates issued for conversion technologies should be 

valid indefinitely and should not expire 

Chew commented that EPA should clarify the length of certificate validity and 

suggested that EPA add language to the certificate such as: “For the clean alternative 

fuel vehicle and engine conversions, each certificate is valid for that (i) specific model 

year, or (ii) prior model years than (i), if no substantial changes have occurred unless the 

CO has been superseded.” 

NGVA commented that this rule only applies to existing vehicles, not new 

vehicles as defined by section 216 of the CAA, which covers vehicles for which the title 

has not been transferred to the ultimate purchaser. Therefore, EPA could establish a 

different definition of model year and different time frame for certificates issued to 

conversion manufacturers who manufacture systems intended for use on used vehicles or 

engines. NGVA recommended that the model year of the certificate should be the year in 

which certificate is granted and the certificate should not expire. 

Our response: 

EPA is maintaining the certification policy as proposed. Nonetheless EPA 

recognizes that converters wish to retain protection against a tampering violation and 

wish to maintain eligibility for tax credits and other programs that rely on a valid 

certificate. 

EPA has determined that the exemption from tampering for qualifying vehicles 

and engines does not end with the expiration of the certificate as long as the conditions 

under which the certificate was issued remain unchanged. The final clean alternative fuel 

25 75 FR 29619 (May 26, 2010). 

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conversions rule provides pathways, including a certification pathway, by which 

converters may secure an exemption from the CAA tampering prohibition. It is EPA’s 

position that once a conversion manufacturer has secured the exemption through 

certification, even though the certificate expires, the exemption does not expire and does 

not need to be renewed each year. 

12.7 Changes Affecting the Economy 

What commenters said: 

Petkov commented that EPA should not make changes that would harm the 

economy. 

Our response: 

EPA projects that this rule will generally reduce the cost of compliance for 

conversion manufacturers and will therefore not have adverse economic effects. 

12.8 Miscellaneous 

What commenters said: 

An anonymous commenter stated that there is no current pathway to convert a 

gasoline powered vehicle to a diesel powered vehicle. 

Our response: 

The clean alternative fuel conversion regulations could be used to demonstrate 

that the conversion of a gasoline to a diesel vehicle qualifies for an exemption from the 

tampering prohibition. 

13. Other comments received 

13.1 Comments Outside the Scope of this Rulemaking 

What commenters said: 

An anonymous comment stated that emissions or safety failures should not be 

indicated by a yellow “Check Engine” maintenance light because the light is assumed to 

pertain to the mechanical operation of the vehicle. The commenter suggested that a safety 

or emissions indicator should say something like “Failed Inspection” so that its purpose is 

not confused with a service reminder. 

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Caterpillar commented that fuel converters should be required to comply with 

EPA’s service information requirements in 40 CFR part 86. 

Reed questioned why the proposal prohibits any remanufacturer/converter from 

seeking EPA certification for remanufactured engines and does not include a pathway to 

apply for and receive EPA certification. 

Our response: 

Regarding the comment about the MIL, the scope of this rulemaking does not 

include making changes to the OBD malfunction indicator light (MIL). EPA took public 

comment on the design aspects of the MIL on September 24, 1991,26 and finalized those 

requirements on February 19, 1993.27 

Regarding the comment on service information availability, section 202(m)(5) of 

the CAA requires vehicle and engine manufacturers to make available to aftermarket 

service providers all information made available to their dealers that is needed for making 

emissions-related diagnoses and repairs. While EPA has generally considered these 

provisions to apply to manufacturers of new motor vehicles and engines, we have not 

thoroughly considered how the service information provisions should apply to alternative 

fuel converters. Because EPA did not propose or seek comment on applying the service 

information to alternative fuel converters, we believe it outside the scope of this 

rulemaking to require that alternative fuel converters comply with the service information 

provisions. Should EPA propose changes to the service information requirements in the 

future, we would consider how these provisions could apply to alternative fuel 

converters. 

Regarding the comment on remanufacturers, remanufacture provisions are 

covered under 40 CFR 86.004-40, and do not fall within the scope of this rulemaking. 

26 56 FR 48272. 27 58 FR 9468. 

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