Hogan Lovells US LLP 

Columbia Square 

555 Thirteenth Street, NW 

Washington, DC 20004 

T +1 202 637 5600 

F +1 202 637 5910 

www.hoganlovells.com 

August 18, 2011 

Karl Simon, Director 

Compliance and Innovative Strategies Division 

Office of Transportation and Air Quality 

United States Environmental Protection Agency 

1200 Pennsylvania Avenue NW 

Washington, DC 20460 

Re: Request for Updated Scheduled Maintenance Intervals for Selective Catalytic 

Reduction Technologies for Model Years 2012 and Later 

Dear Mr. Simon: 

 Pursuant to 40 C.F.R. § 86.094-25(b)(7)(ii), Chrysler Group, LLC, Cummins Inc., Daimler 

Trucks North America LLC, Detroit Diesel Corporation, Ford Motor Company, Mack Trucks Inc., 

PACCAR Inc., UD Trucks Corporation, and Volvo Group North America, LLC, (collectively the “SCR 

Engine Manufacturers”) hereby request revised scheduled maintenance intervals for SCR 

technologies for model years 2012 and later. Specifically, the SCR Engine Manufacturers request 

that EPA approve the use of the 1:1 diesel exhaust fluid (DEF) to fuel ratio for vehicles with a DEF 

level indicator, in addition to vocational vehicles, and that EPA grant its approval of the reduced SCR 

maintenance intervals for an indefinite time period or until a point in time when there is compelling 

evidence that the DEF replenishment interval should be revisited.1

 This approval is necessary and 

appropriate to reflect current and anticipated changes in vehicle designs, significant changes in 

inducement strategies, and the increased availability of DEF that have arisen since EPA’s November 

9, 2009 Approval of New Scheduled Maintenance for Selective Catalyst Reduction Technologies 

(the “2009 Notice”).2

I. Applicable Regulatory Requirements

 

1

 For the SCR Engine Manufacturer companies, this request updates their position from that contained in 

the earlier Engine Manufacturers Association’s renewal request dated June 13, 2011. For all of the 

reasons set forth in this petition, the SCR Engine Manufacturers suggest that the distinction based on the 

presence of a constantly viewable DEF level indicator (for the 3:1 ratio) is unnecessary. The many 

warnings and inducements that manufacturers have built into their vehicles obviate the need for this 

distinction. 

2

 Control of Emissions from New Highway Vehicles and Engines: Approval of New Scheduled 

Maintenance for Selective Catalyst Reduction Technologies, 74 Fed. Reg. 57,671 (Nov. 9, 2009). 
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Based on certain conclusions in the 2009 Notice, EPA requires manufacturers to petition the 

Agency under 40 C.F.R. § 86.094-25(b)(7)(ii) (hereafter, just “(b)(7)”) for approval of DEF refill rates 

that are less than the standard regulatory interval for catalyst replacement or maintenance (150,000 

miles, or 4,500 hours, for medium and heavy heavy-duty diesel engines).3

 Section (b)(7) sets forth 

the required contents of a petition for an alternative maintenance interval, and establishes the 

threshold criteria EPA will use to determine whether an interval shorter than the regulatory default 

will be approved. 

A. Content of the Petition 

A petition for an alternative maintenance interval under (b)(7) must include the following five 

pieces of information from the petitioning manufacturers: 

i) Need for Maintenance: an explanation of why the maintenance is “technologically necessary 

to assure in-use compliance with the emission standards”;4

ii) Category Recommendation: a recommendation as to whether the maintenance is emissionrelated or non-emission-related, critical or non-critical;5

iii) Maximum Feasible Interval Reference Point: information on “the maximum feasible 

maintenance interval”;6

iv) Recommended Interval: the specific “interval suggested” by the manufacturers;7

 and 

v) Other Information Supporting Reasonableness of Suggested Interval: “supporting data or 

 

3

 In the 2009 Notice, EPA indicated that the replenishment of DEF is either the “adjustment, cleaning, 

repair, or replacement” of the “catalytic converter” or an “add on emissions-related component,” which 

would make DEF refills subject to these maintenance regulations. 74 Fed. Reg. at 57,672; see 40 C.F.R. 

§ 86.004-25(b)(4)(iii). DEF replenishment is not typical maintenance, nor “adjustment, cleaning, repair, or 

replacement,” and is more clearly analogous to periodic vehicle refueling. The concept of DEF 

replenishment is also not included in the words used to define “scheduled maintenance” at 40 C.F.R. 

§ 86.084-2, which states that it means “adjustment, repair, removal, disassembly, cleaning, or 

replacement of vehicle components or systems which is performed on a periodic basis to prevent part 

failure or vehicle (if the engine were installed in a vehicle) malfunction, or anticipated as necessary to 

correct an overt indication of vehicle malfunction or failure for which periodic maintenance is not 

appropriate.” Given that the maintenance regulations were simply not written to contemplate an 

emissions control technology whose normal operation requires replenishment of a consumable, the SCR 

Engine Manufacturers have participated in the (b)(7) process as a mechanism for working with the 

Agency to introduce a new form of emissions control, in a spirit of constructive cooperation. 

4

 40 C.F.R. § 86.094-25(b)(2), (b)(7)(ii). 

5

 40 C.F.R. § 86.094-25(b)(7)(ii). 

6 Id.

7

 Id.
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other substantiation” for the interval suggested, which becomes a part of the “industry data and 

any other information available to EPA” that enables EPA to establish “a technologically 

necessary maintenance interval.”8

Much of this information was submitted with the initial 2009 (b)(7) petition and was confirmed by 

EPA’s 2009 Notice, and therefore needs no further elaboration here. Specifically, EPA has already 

concluded that replenishment of DEF is “technologically necessary” critical emission-related 

maintenance, and that the 1:1, 2:1, and 3:1 ratios were “maximum feasible” maintenance intervals 

based on information available in 2009. There has been no change in either the need for DEF 

replenishment or designation of the category of maintenance since 2009. This petition asserts that 

the 1:1 DEF to fuel ratio now reflects the maximum feasible interval based on reasonable tank sizes, 

given the latest information available regarding SCR systems and DEF availability. 

B. Threshold Criteria for Approval of Reduced Maintenance Interval 

The regulations also provide that EPA will set “a technologically necessary maintenance 

interval.”9

 The general maintenance regulations provide further guidance on what “technologically 

necessary” means where they provide that “[a]ny emission-related maintenance” “must be 

technologically necessary to assure in-use compliance with the emission standards.”10 Thus, under 

(b)(7), EPA first makes a threshold determination that the manufacturers’ recommended scheduled 

maintenance, at an interval shorter than the regulatory default, is “technologically necessary to 

assure in-use compliance with the emission standards.”11

II. EPA’s 2009 Conclusions

 While the (b)(7) regulations establish what information must be included in a petition and that 

a reduced interval will only be granted for maintenance that is “technologically necessary” to assure 

in-use compliance with the emission standards, EPA’s 2009 Notice established the specific factors 

that EPA uses to determine what a reasonable and appropriate technologically necessary interval is 

for DEF replenishment. The (b)(7) regulations were originally developed to address mechanical 

engine technology that is subject to wear, but which is expected to last the full useful life of a vehicle, 

or a significant portion of that useful life. In contrast to those mechanical maintenance items, SCR 

systems use a consumable that is subject to regular periodic replenishment by design. The 2009 

Notice specifically addressed the unique nature of liquid DEF replenishment, and the need to strike a 

reasonable balance between conflicting design goals. In doing so, the 2009 Notice established that 

EPA’s determination is based on the “approximate” “maximum feasible maintenance intervals 

 

8

 Id. (emphasis added). 

9 Id. (emphasis added). 

10 40 C.F.R. § 86.094-25(b)(2). 

11 Thus the maintenance itself must be technologically necessary for compliance. EPA’s 2009 Notice 

established that the replenishment of DEF tanks at an interval of less than 150,000 miles, or 4,500 hours, 

is in fact “technologically necessary” to assure in-use compliance. 74 Fed. Reg. at 57,673. 
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associated with reasonable DEF tank sizes.”12 More specifically, EPA’s Notice discussed several 

key factors that EPA uses to determine what is reasonable and appropriate, and explained how each 

is used in the (b)(7) process. 

 A. Technological Necessity of an Interval Less Than 150,000 Miles (or 4,500 Hours)

 The regulations use the words “technologically necessary” in two contexts. First, section 

(b)(2) requires that all maintenance that meets the definition of “emission-related maintenance” 

“must be technologically necessary to assure in-use compliance with the emission standards.”13 

Consistent with this provision, (b)(7)(ii) requires that any alternative interval set by EPA be “a

technologically necessary maintenance interval.”14 In other words, once some reduced maintenance 

interval has been found to be technologically necessary, EPA may only approve an interval that is 

reasonable and appropriate, in its discretion, based on the information submitted, and other 

available facts. Thus, the words “technologically necessary” describe the category of maintenance 

that is allowable, but they do not describe what the specific interval must be. The 2009 Notice 

clearly established that the periodic refilling of DEF (at less than 150,000 miles, or 4,500 hours) is 

necessary for SCR technology to assure that emission standards are met in-use.15 In conclusion the 

Agency stated: “EPA agrees with manufacturers that the DEF refilling intervals requested are 

technologically necessary. EPA knows of no SCR technology for any heavy-duty engine application 

that is yet capable of attaining higher mileage without a DEF refill.”16 DEF replenishment remains as 

“technologically necessary” today as it was in 2009, and EPA should continue to allow DEF refills at 

a frequency of less than 150,000 miles, or 4,500 hours. 

 Once the “technologically necessary” threshold determination is made for setting a shorter 

interval, EPA then evaluates the information in the petition, including: i) the maximum feasible 

interval, ii) the suggested interval, and iii) “other information” to establish the new alternative interval. 

EPA’s regulations do not require that it set alternative maintenance intervals at the maximum level 

that is technologically feasible. The term “feasible” requires EPA to look at the overall practicality 

and reasonableness of a particular proposed interval. The maximum feasible interval is used as a 

point of reference to enable EPA to evaluate the reasonableness of the manufacturers’ 

recommended interval. The maximum possible interval for DEF replenishment is established in 

each case by the total load capacity of the vehicle in question, the space available for a given DEF 

tank size, the fuel efficiency and GHG impact of various DEF dosing rates, the desired operating 

range of the vehicle between fuel and DEF refills, and the impact of extra weight on vehicle 

performance, safety, and compliance with U.S. Department of Transportation regulatory 

requirements. DEF tank size must also be balanced against the need to carry cargo, or to enable 

the vehicle to meet the purpose for which it was built, to determine what is feasible in the most 

economical way possible while achieving compliance. In EPA’s 2009 Notice, EPA explained that 

 

12 74 Fed. Reg. at 57,674 (emphasis added). 

13 40 C.F.R. § 86.094-25(b)(2). 

14 40 C.F.R. § 86.094-25(b)(7)(ii) (emphasis added). 

15 74 Fed. Reg. at 57,672, 57,673-74. 

16 Id. at 57,673. 
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while it may be possible for a line-haul truck to carry the 750-900 gallons of DEF needed to operate 

for the entire 150,000 mile interval, it would be entirely unreasonable to require the truck to carry 

6,750 or more pounds of DEF, because that would reduce cargo capacity by 15% or more.17 In 

short, the 2009 (b)(7) process made it clear that the reduced maintenance interval would never be 

set at the maximum possible interval. Instead, EPA must set a reasonable, feasible interval, in its 

discretion, based on a variety of factors and all available information. 

 B. Likelihood of Being Performed In-Use 

 The 2009 Notice established that once the technological necessity of a lesser interval has 

been determined, the likelihood of being performed in-use is the most important factor in establishing 

the precise maintenance interval. First, EPA explained that “minimum service intervals are 

established in part to ensure that the control of emissions is not compromised by a manufacturer’s 

overly frequent scheduling of emission-related maintenance.”18 Excessive frequency can only 

compromise emissions control where it creates a risk that the maintenance will not be performed inuse. 

 Second, EPA explained that while likelihood of being performed in-use was a specific criteria 

under (b)(6), it was also a factor that was “important to note” with regard to EPA’s (b)(7) findings, 

particularly with regard to “critical emission-related maintenance.”19 EPA then concluded that it was 

“reasonable to base the DEF refilling event on diesel refueling intervals given that it is likely that the 

DEF refill maintenance would be undertaken at the time of fuel refill due to DEF infrastructure 

developed at diesel refueling stations.”20

 Most importantly, EPA used the likelihood of performance in-use as the exclusive factor for 

determining which of the three alternative maintenance intervals would be applicable to a particular 

type of heavy-duty on-highway (“HDOH”) vehicle. Specifically, EPA established three allowable 

maintenance intervals in 2009 that were expressed as a ratio of the DEF tank range to the fuel tank 

range, specifically 1:1, 2:1, and 3:1. The only relevant difference between the applications eligible 

for the three different intervals is the likelihood of being refilled in-use. Specifically, centrally fueled 

vocational vehicles were expected to be the most likely to be refilled in-use, and the interval was set 

at 1:1. Vehicles with a constantly viewable DEF level indicator were anticipated to be the next most 

likely to be refilled, and the interval was set at 2:1. Finally, vehicles without a constantly viewable 

level indicator were thought to be less likely to be regularly filled than the other categories, and a 

longer interval of 3:1 was established. 

 C. Other Data and Information

 As noted above, (b)(7) requires EPA’s determination to be “based on industry data and any 

 

17 74 Fed. Reg. at 57,673. 

18 Id. at 57,672. 

19 Id. at 57,673. 

20 Id. 
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other information available to EPA.”21 EPA’s 2009 Notice focused on two relevant categories of 

other industry data: (1) the technological feasibility of different DEF tank sizes; and (2) the availability 

of DEF to on-highway users. EPA made two related findings of fact that remain accurate today. 

First, EPA concluded that DEF tank sizes were limited by weight and space constraints, and that 

tanks larger than those recommended by manufacturers were not reasonably feasible. Specifically, 

DEF tanks capable of a 150,000 mile range were “clearly not technologically feasible in light of the 

weight and space demands and constraints on heavy-duty trucks.”22 EPA also explained that 

“longer intervals than those requested by the manufacturers would require DEF tanks that are too 

large or too heavy to be feasibly incorporated into vehicles. . . . Because of inherent space and 

weight constraints in the configuration and efficient operation of heavy-duty vehicles, there are size 

limits on the DEF tanks.”23 In addition, EPA also focused on DEF availability in concluding that it 

was “reasonable to base the DEF refilling event on diesel refueling intervals given that it is likely that 

the DEF refill maintenance would be undertaken at the time of fuel refill due to DEF infrastructure 

developed at diesel refueling stations.”24

 Thus, although the phrase “likelihood of being performed in-use” is not used in (b)(7), the 

SCR Engine Manufacturers agree that that has been, and should continue to be, the primary factor 

in EPA’s assessment of what a reasonable proposed maintenance interval for DEF replenishment 

should be. 

III. Significant Changes to Key Factors Have Occurred Since 2009, All of Which Support 

Expanded Use of the 1:1 Tank Ratio

 The 2009 Notice recognized that EPA’s initial (b)(7) approval may need to evolve as DEF 

infrastructure and SCR technology change over time. EPA explained the following: 

The Agency has limited this approval to model years 2009 to 2011 due to the 

expectation that SCR-related technologies and the urea infrastructure will continue 

to develop and mature, and EPA plans to revisit this category of vehicles to 

determine appropriate future intervals. Should manufacturers continue to believe 

that the identified interval or other intervals are technologically necessary or 

otherwise appropriate after the 2011 model year, we expect them to take this up with 

the Agency in a timely manner.25

Significant changes have occurred with respect to each of these key factors, as discussed below. In 

each case, the changes support the expanded use of the 1:1 tank ratio as requested by the SCR 

Engine Manufacturers. 

 A. Likelihood of Being Performed In-Use 

 

21 40 C.F.R. § 86.094-25(b)(7)(ii). 

22 74 Fed. Reg. at 57,673. 

23 Id. 24 Id. 25 Id. at 57,674 (emphasis added). 
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 In the 2009 Notice, EPA indicated that it expected that in most cases, DEF would be refilled 

at each refueling stop.26 Two developments since 2009 have further increased the likelihood of DEF 

replenishment at each and every refueling stop: (1) more severe inducement strategies; and (2) 

increased availability of DEF. 

1. More Severe Inducements 

EPA’s 2011 Draft SCR Guidance27 on SCR inducement strategies makes it essentially 

impossible for an SCR vehicle to operate without regular DEF replenishment. Although this is also 

true of vehicles certified under earlier guidance, the dramatic increase in the severity of DEF level 

inducements from 2009 to the present is extraordinary and must be taken into account in approving 

updated maintenance intervals. 

 Under the December 2009 SCR Guidance,28 EPA stated that “[i]n determining strategies that 

are sufficiently onerous to cause the driver to replenish the DEF tank and minimize any adverse 

emission impact, manufacturers can consider strategies that begin to degrade performance prior to 

the DEF tank being empty and that progressively become more onerous as the DEF tank becomes 

empty.” EPA further explained: “Possible approaches for the manufacturer to degrade performance 

include a derate of the engine’s maximum available engine torque of a sufficient magnitude for the 

operator to notice decreased operation (a derate of at least 25% is likely to be needed for such an 

effect) and progressing to further degradation that could include operation of the engine being 

disabled or severely restricted, implemented in a manner designed to prevent operation without DEF. 

EPA recognizes that there may be safety concerns regarding a complete disablement of the engine 

or severe degradation occurring while the vehicle is moving, and therefore believes that such 

degradation would best be initiated at the time of refueling, parking or restart.”29

 In the 2011 Draft SCR Guidance, EPA proposes that, when the DEF tank is empty, final 

inducement consisting of a 5 mph maximum vehicle speed or engine shutdown / idling-only limitation 

be imposed while the vehicle is in operation.

30 If manufacturers choose to implement final 

inducement only when the vehicle is stopped in a safe location (identified by a refueling, 60-minute 

idling, or key-off event), they must design their engines to meet additional characteristics, which 

include imposition of a severe inducement prior to triggering final inducement. “The severe 

inducement will consist of an engine derate, a vehicle speed limitation, or a limitation on the number 

of engine restarts.”31 EPA provides, as an example of an acceptable severe inducement, an engine 

 

26 The 2009 Notice explained that “operators are expected to refill the DEF a[t] each diesel fuel refilling 

event.” 74 Fed. Reg. at 57,674. 

27 Control of Emissions from New Highway Vehicles and Engines; Guidance on EPA’s Certification 

Requirements for Heavy-Duty Diesel Engines Using Selective Catalytic Reduction Technology (“2011 

Draft SCR Guidance”), 76 Fed. Reg. 32,886 (June 7, 2011). 

28 Revised Guidance for Certification of Heavy-Duty Diesel Engines Using Selective Catalyst Reduction 

(SCR) Technologies (“December 2009 SCR Guidance”), CISD-09-04 REVISED, at 5 (Dec. 30, 2009). 

29 Id.

30 76 Fed. Reg. at 32,894. 

31 Id. (emphasis added). 
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torque derate of 40 percent, which should occur when there is enough DEF in the tank to last one 

full day of operation, or with 10 percent reserve in the tank.32

 In addition, in light of these severe inducements, it is reasonable to expect that a driver with 

a 1:1 tank ratio will operate under a firm discipline that the DEF tank must be refilled every time the 

fuel tanks are filled, as opposed to a driver with a 2:1 or greater tank ratio who may become 

accustomed to filling the DEF tank only when necessary, and is therefore more likely to rely on 

gauge levels, warnings, and inducements to trigger refills. 

2. Increased Availability of DEF 

In 2009, centrally fueled fleet vehicles were viewed as the most likely to have DEF available 

at each refueling stop. DEF infrastructure has developed significantly since 2009. Today, DEF is as 

readily available at truck stops and other refueling locations as it was previously expected to be at 

central fleet refueling centers. Therefore there is no longer any reason to distinguish between 

centrally fueled operations and line-haul operations from a DEF availability perspective. As EPA 

noted in its 2011 Draft SCR Guidance: “DEF infrastructure and sales volume have continued to 

grow since introduction of 2010 model year trucks equipped with SCR systems. . . . DEF is now 

available for sale in every state at truck stops and service facilities, and is available for delivery to 

fleet locations, as well.”33 EPA also stated: “The continually increasing DEF infrastructure and sales 

volume have resulted in improved DEF availability along major truck routes as well as other 

locations. . . . Increasing demand supported by sales volume helps drive the continuing expansion 

of DEF infrastructure.”34 With widespread availability of DEF, drivers can refill their DEF tanks at the 

same time that they refuel with diesel, so that a 1:1 ratio is now as appropriate for vehicles with a 

DEF level indicator as it is for vocational vehicles. 

 B. Feasibility of Other Tank Sizes 

 In the 2009 Notice, EPA concluded that the specific tank sizes associated with the 1:1, 2:1, 

and 3:1 ratios were the maximum reasonably feasible “in light of the weight and space demands and 

constraints on heavy-duty trucks.”35 EPA explained that: 

Because of inherent space and weight constraints in the configuration and efficient 

operation of heavy-duty vehicles, there are size limits on the DEF tanks. 

. . . The extra weight associated with the DEF required to meet the 2:1 or 3:1 refill 

intervals . . . represents a significant challenge to manufacturers seeking to meet 

both weight and size requirements for their vehicle designs. EPA believes that in 

light of the existing tight space constraints and the overall desire to maximize cargocarrying capacity to minimize emissions and meet consumer operational demands, 

and the built-in DEF tank size buffer to insure DEF refills, that the DEF tank sizes 

associated with the 2:1 and 3:1 refill intervals are technologically necessary. EPA 

 

32 Id.

33 76 Fed. Reg. at 32,887. 

34 Id. at 32,891. 

35 74 Fed. Reg. at 57,673. 
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believes that requiring tank sizes above these ratios will cause increases in space 

constraints and weight that would not be appropriate for these vehicles. 

. . . EPA believes that longer refill intervals than those noted above would require 

larger and heavier DEF tanks, and the design and engineering work performed by 

manufacturers thus far indicate that the recommended DEF refill intervals noted 

above approximate the maximum feasible maintenance intervals associated with 

reasonable DEF tank sizes.36

 As noted above, the only reason EPA had for imposing the greater burden of 2:1 and 3:1 

tank ratios on manufacturers was the belief that those vehicles had a lower likelihood of being 

refilled in-use than vocational trucks. Because that is no longer true, the 1:1 tank ratio would be the 

maximum reasonably feasible DEF tank size for other vehicles with an equal likelihood of being 

refilled in-use. 

C. Impact of New HDOH GHG Standards 

 

 Several significant regulatory and engineering developments since 2009 have further 

increased the size and weight constraints associated with the previously approved tank sizes. First, 

EPA has announced new fuel economy standards for HDOH trucks, and manufacturers have moved 

to voluntarily increase the fuel efficiency of their vehicles in advance of the effective dates of those 

regulations. 37 Within these regulations, EPA recognizes the impact of weight savings on fuel 

efficiency and GHG emissions. In addition, manufacturers have developed innovative new DEF 

dosing strategies to reduce CO2 emissions. These new strategies may involve increasing the DEF 

dosing rate. Increasing the DEF dosing rate also makes it more and more difficult to satisfy a 2:1 

tank size ratio without increasing the size of the DEF tank above the size EPA previously considered 

the maximum reasonable size. For this reason, if the application of the 1:1 tank ratio is not 

expanded, EPA will effectively be mandating larger DEF tanks, with their accompanying weight 

increase, in order to accommodate technology advancements developed to reduce CO2 emissions—

tanks that are larger than the tanks EPA determined to be the maximum reasonably required in 2009. 

In addition, this could inadvertently cause manufacturers to restrict application of the most fuel 

efficient engines to vehicles that have reduced range between fuel and DEF refills, such that they 

will be unattractive to the line-haul fleets that consume the most fuel. 

 In addition, future GHG requirements that will take effect (2013 for the early compliance 

option) in the time frame of the requested approval will also make it increasingly difficult to 

accommodate 2:1 tank sizes in line-haul truck applications. Specifically, improved aerodynamics 

and excess weight reductions are critical to meeting the upcoming GHG requirements. Requiring 

trucks to carry completely surplus DEF, and increasing that burden, simply cannot be justified in the 

face of EPA’s new GHG requirements. 

Allowing manufacturers greater flexibility in sizing their DEF tanks has analogies with other 

fuel efficiency improvement and GHG emission reduction strategies. With the 1:1 ratio option, 

 

36 Id. at 57,673-74. 

37 See Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and HeavyDuty Engines and Vehicles, 75 Fed. Reg. 74,152 (proposed Nov. 30, 2010). 
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manufacturers who choose to reduce their DEF tank sizes will realize a corresponding weight 

reduction.38 EPA has recognized that reductions in vehicle mass, such as by reducing the size of 

the DEF tank and amount of excess DEF carried, reduce fuel consumption and GHG emissions: 

“Reductions in vehicle mass reduce fuel consumption and GHGs by reducing the overall vehicle 

mass to be accelerated and also through increased vehicle payloads which can allow additional tons 

to be carried by fewer trucks consuming less fuel and producing lower emissions on a ton-mile 

basis.”39 For example, EPA has noted that a change in tire design can result in a significant weight 

reduction: “A tractor’s empty curb weight can be reduced from the replacement of dual tires with 

single wide tires and with the replacement of steel wheels with high strength steel or aluminum. 

Analysis of literature indicates that there is opportunity to reduce typical tractor curb weights by 80 to 

670 pounds, or up to roughly 3 percent, through the use of lighter weight wheels and single wide 

tires . . . .”40

 Manufacturers need to be able to use the full array of available options to meet the newly 

finalized GHG standards and to improve the real-world fuel economy for their HDOH customers 

(including off-cycle operations). EPA’s policies should allow—if not encourage—increased DEF 

dosing, which can provide a significant CO2 benefit (for example, by allowing manufacturers to 

reduce the use of EGR). Increased dosing means increased DEF tank sizes unless the 

maintenance intervals are adjusted. Not only would increased DEF tank sizes be larger than those 

previously found to be the maximum feasible, but they would work against the CO2 benefits 

manufacturers are trying to attain, by adding weight and making it harder to achieve improved 

aerodynamics. With all of the SCR warnings and inducements that have been required since the 

2009 petition was granted, the importance of maintaining any particular tank ratio is now negligible. 

It is critical that EPA not tie manufacturers’ hands on CO2 improvement by imposing arbitrary policies 

on issues of lesser importance, working at cross-purposes to the goal of CO2 reduction. 

IV. The SCR Engine Manufacturers’ Requests

 A. Request for Broader Use of the 1:1 Tank Ratio 

 For all of the reasons set forth above, the SCR Engine Manufacturers hereby request that 

the 1:1 tank ratio be approved for vehicles that have a constantly viewable DEF level indicator, just 

as this tank ratio was previously approved for vocational vehicles. In addition to the reasons set 

forth above, there are additional policy considerations that favor granting this request. 

 First, in some cases, manufacturers will continue to use the same 2:1 DEF tanks that have 

already been engineered into existing models, and will use the 1:1 maintenance interval simply to 

allow increased DEF dosing to improve GHG emissions. In these trucks, the actual tank size ratio 

will be somewhere between 1:1 and 2:1 (for example, 1.8:1). Alternatively, some manufacturers 

 

38 For example, on a line-haul truck with a 300 gallon diesel fuel capacity, assuming a 3% DEF 

consumption rate, an 18 gallon DEF tank is the minimum required with the 2:1 maintenance interval. 

However, if the 1:1 maintenance interval is approved, the DEF tank could be as small as 9 gallons, for a 

weight savings of 81 pounds (assuming a DEF density of 9 lb/gal) compared to the 18 gallon tank. 

39 75 Fed. Reg. at 74,216. 

40 Id. at 74,217. 
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may use the 1:1 maintenance interval in order to achieve weight reductions and improve GHG 

emissions by offering combinations of DEF and fuel tank sizes that are not allowed with the 2:1 

maintenance interval, as described in section III.C. 

 In addition, an extraordinary investment of time and capital has been made to develop 

today’s inducement strategies. EPA should recognize this investment, and the increased efficacy of 

the latest inducements by allowing the broader use of the 1:1 tank ratio. Allowing this flexibility, 

which is perfectly consistent with EPA’s regulations and past decision-making would enable 

manufacturers to focus their resources on CO2 reduction developments, rather than requiring the reengineering of DEF tanks that are already over-engineered for the current generation of vehicles, 

given the latest inducements and current wide availability of DEF. 

 B. Request to Extend the Approval of Updated Scheduled Maintenance Beyond 

 Two Model Years 

 The SCR Engine Manufacturers request that EPA grant its approval for the reduced SCR 

maintenance intervals for a period longer than two model years and recommend an approval 

remaining effective indefinitely (until such time as compelling evidence may indicate that the DEF 

replenishment interval should be revisited). A longer approval time period would provide greater 

certainty for manufacturers for planning and design purposes, thereby reducing costs and improving 

design development, and it would reduce the administrative burden on the agency. It would be 

beneficial for both manufacturers and EPA not to have to renew the (b)(7) petition and approval 

process every two years. 

* * * 

 We look forward to your response to this request. Please contact us if we can provide any 

additional information. 

Sincerely, 

R. Latane Montague 

Partner 

latane.montague@hoganlovells.com 

D 202.637.6567