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Technical Memorandum

From: Robert Anderson, Environmental Protection Agency

To: Docket EPA-HQ-OAR-2009-0211

Date: 10/XX/2010

Subject: Technical Summary of DOE Study on E15 Impacts On Tier 2 Vehicles

and Southwest Research Teardown Report 

The purpose of this technical memorandum is to: (1) outline in more detail the research 

study design of the recently completed Department of Energy (DOE) E0 and E15 catalyst 

durability test program (DOE V4 program hereafter); (2) explain in more detail analyses that 

were used as a basis for the partial waiver decision evaluating the data obtained from the DOE 

V4 program; (3) summarize the results of the engine teardown report that the Southwest 

Research Institute (SwRI) completed for DOE on several vehicles tested in DOE V4 program; 

and, (4) explain how non-methane organic gas (NMOG) emissions were estimated for use in the

analyses for the partial waiver decision. 

1 –Study Design – DOE V4 Program

The DOE V4 program was established to investigate the potential impacts of gasolineethanol blended fuels containing greater than 10 volume percent (vol%) on the durability of 

vehicle emissions control systems. The program began with a subcontracted effort at Southwest 

Research Institute (SwRI) in San Antonio, Texas and was later expanded and accelerated by

placing additional subcontracts to perform portions of the needed work at Transportation 

Research Center (TRC) in East Liberty, Ohio, and Environmental Testing Corporation (ETC) in 

Aurora, Colorado. The SwRI and TRC subcontracts and technical work was managed by Oak 

Ridge National Laboratory (ORNL), while the ETC subcontract and technical work was 

managed by the National Renewable Energy Laboratory (NREL). The scope-of-work for each 

subcontract differed in some details (such as the number of fuels being evaluated) but were 

generally the same in terms of the methodology of the program.

Vehicle Selection and Matching

There were a number of relevant criteria that determined the selection of vehicle models 

for the program. These included whether a vehicle model was Tier-2 compliant, manufacturer, 

sales/registration volumes, and whether a vehicle model did or did not apply learned fuel trim 

(LFT or non-LFT, respectively) at wide-open throttle (WOT). Several studies provided

information that impacted selection: EPA’s EPACT vehicle study at SwRI, Coordinating 

Research Council’s (CRC) E87-1 study, and DOE’s previous 16 vehicle screening study. Based 

on the vehicle set EPA used to represent the Tier 2 fleet in its EPAct program, DOE instructed 

the national laboratories to use similar criteria in selecting a vehicle set for long-term durability

studies.1 The make and model of 18 of the 19 vehicles tested were identical to the makes and 

 

1 EPA selected vehicles for its EPAct study based on several criteria. The Agency selected vehicles based on MY 

engine family sales data since there are usually multiple models to choose from for each engine family. 

Additionally, EPA focused on high volume sellers since, by definition, high volume sellers are representative and 

eases recruitment.
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models of the 19-vehicle EPAct test vehicle fleet. However, at the request of CRC, DOE 

substituted the Nissan Quest for a Toyota Sienna. DOE also choose to have the model years 

(MY) of the test fleet vehicles range from MY2005-MY2009 instead of just using MY2008 

vehicles that EPAct utilized. Additionally, the sample size and vehicle selection methodology of 

this program conforms to EPA guidance necessary to conduct a long-term durability test 

program.2

Matched sets of vehicles were needed to accomplish the desired testing program. The 

vehicle sets were matched to prevent confounding of the data by undesirable vehicle attribute 

changes. Specifically, the engine family, engine displacement, evaporative emissions control 

family, model year, powertrain control unit calibration, axle ratios, wheel size, and tire size were 

constrained to be identical within a vehicle set. Physical inspections of the vehicles to eliminate 

obvious problematic vehicles (such as those with gross fluid leaks, obvious and excessive body 

damage, etc) were also a part of the selection of vehicles for the matched sets. Odometer reading 

was also used to identify candidate pre-owned vehicles with the goal of restricting the range of 

odometer readings within a vehicle set to a maximum of 10,000 miles. One vehicle from each 

set was aged and tested on E0 and E15.3

 

2

See EPA Docket #EPA-HQ-OAR-2009-0211-2559.2, API Technology Committee Meeting, Chicago, 6/4/08.

3 The number of vehicles in a matched set varied during the test program according to the number of fuels being 

targeted for test. In some cases four ethanol blend levels were tested (E0, E10, E15, and E20), while in other cases a 

subset of these fuels were tested. Since the waiver request is for E15, this analysis focuses on those vehicles that 

were aged on E15 compared to those vehicles that were aged on E0.
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Table 1. Vehicle attribute summary.
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The assignment of a particular vehicle to a particular fuel was random and was 

accomplished prior to any emissions tests being conducted on the vehicles. Table 1 provides 

information on the test vehicles in the program. Obtaining suitable matched sets of vehicles was 

challenging for several of the older model year vehicles in the program. For this reason, there 

were a few instances where it was necessary to compromise the 10,000 mile odometer range 

target in order to obtain an otherwise suitably-matched set of vehicles.

Fuels and Blending

The fuels used at the several test sites were obtained commercially by the subcontractors. 

In all cases, for both emissions certification and aging fuels, the ethanol-containing fuels were 

splash-blended.

Emissions and related tests were conducted using emissions certification gasoline (E0) or 

E15 blended from emissions certification gasoline and denatured fuel-grade ethanol. These 

batches were subsequently analyzed to provide the information necessary to conduct the 

program. These analyses included: the actual ethanol content of the batch; carbon; hydrogen 

and oxygen fractions; and, density. Whenever possible, large enough batches to complete the 

several phases of the program were produced to reduce potential batch-to-batch effects on the 

results of the program.

Aging fuels were produced by blending denatured fuel-grade ethanol with gasoline (E0)

commercially available at retail stations, rather than emissions certification gasoline, in order to 

control costs. (Many thousands of gallons of aging fuel were used in the program.) Batches of 

E15 used for vehicle aging were analyzed for assurance that they contained the correct amount of 

ethanol. These fuels were not, in general, subjected to the same level of analysis that was 

required for the emissions test fuels at these sites.

Emissions Test Protocol

The vehicles were subjected to an initial emissions test (Federal Test Procedure (FTP)) to 

assure that they were emissions-compliant before acceptance into the program. Once in the 

program, vehicles were subjected to emissions and related tests at the beginning of mileage 

accumulation, at least one mid-mileage point (two points for vehicles at ETC), and at the end of 

mileage accumulation. At SwRI and TRC, the acceptance tests also included tests at wide-open 

throttle to aid in classifying the vehicles as either LFT or non-LFT vehicles. At each emissions 

test interval, duplicate FTP tests were conducted on each vehicle using both E15 and E0. (i.e. 

the E15 vehicle received duplicate FTPs on both E15 and E0.) Wide-open throttle tests were 

also conducted at each emissions test interval with the same fuels as the FTP tests. The vehicles 

also underwent compression and leak-down checks on each engine cylinder at each emissions 

interval.

For the pre-owned vehicles, the vehicles’ initial mileage was dictated by market 

availability and varied considerably, with more recent model years having a lower mileage at the 

beginning of the program. Emissions test and mileage accumulation intervals are based on the 

highest odometer reading in a given vehicle set. The new cars typically had a few hundred miles 
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of difference from the highest to lowest odometer reading in a vehicle set. However, the used 

cars had larger differences, typically several thousand miles. As an example, a set of vehicles 

with mileages of 32,000, 35,000, and 38,000 would experience end-of-program emissions tests 

as the highest mileage car reached 120,000 miles. Thus, the two remaining vehicles in the set 

would experience end-of-program emissions tests at lower mileages (114,000 and 117,000 miles 

respectively.) Mid-aging test intervals were determined in the same way. In this way, the 

overall mileage accumulation experienced by the vehicles in a given set was the same regardless 

of the fuel being used. This method was used because it allowed any fuel effects that were 

identified to be characterized based on equivalent mileage accumulation. This same procedure 

was used with new cars as well, though the mileage differences within a vehicle set are slight for 

these vehicles compared with those typical of the used car sets.

Tier 2 compliant vehicles were driven up to their statutory full-useful life (120,000 

miles). The initial mileages of the Tier 2 vehicles were about 50,000 or lower, meaning that 

these vehicles were driven approximately 70,000-120,000 miles during the program. Emissions 

intervals were determined based in part on the initial mileage of the vehicles. 

New cars were first subjected to aging to an odometer reading of 4,000 miles on retail E0

to stabilize the engine and emissions control systems, followed by the emissions test for 

acceptance into the program and the initial emissions test sequence. Following these tests, these 

cars were subjected to mileage accumulation until approximately 60,000 miles on the odometer, 

at which point the first mid-aging emissions tests were conducted. This cycle was then repeated 

at approximately 90,000 miles for the vehicles under test at ETC for a second mid-aging 

emissions test series. At TRC and SwRI, the 90,000 mile emissions tests were not conducted. 

End-of-aging tests were conducted for all new vehicles at odometer readings of 120,000 miles. 

Pre-owned vehicles were similarly subjected to initial acceptance tests, then initial 

emissions tests, followed by mileage accumulation. Vehicle sets with nominally less than 70,000 

miles at the start of the program were subjected to mid-aging emissions tests at 95,000 miles, 

followed by end-of-aging tests at 120,000 miles. Vehicle sets with nominally more than 70,000 

miles were driven 25,000 miles prior to the mid-aging emission test and an additional 25,000

miles to the end-of-program emissions tests. An exception to this schedule was the Nissan 

Quest, for which the mid-aging emissions tests were dropped from the program at DOE’s 

direction to accelerate completion of the program for this vehicle model.

Mileage Accumulation

The standard road cycle (SRC) was used for all aging. The SRC is the official EPA 

driving cycle used for aging in the whole vehicle exhaust durability procedure. This is a 

recommended EPA procedure that the manufacturers regularly use for verifying full useful life 

emissions capability. It has an average speed of 46.3 miles per hour (mph) and a maximum of 75 

mph. The Nissan Quest aging was changed part way through aging to a series of steady speed 

laps on the test track at TRC at the DOE’s direction to accelerate completion of this vehicle set.

Vehicles under test at TRC were aged using a closed test track. At this site, drivers 

followed the SRC as they drove the vehicles around the track. (Signs were installed at various 
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locations around the track to assist the drivers in following the SRC protocol.) At ETC and 

SwRI, the mileage accumulation was accomplished by using mileage accumulation 

dynamometers (MADs). When a MAD is used, a mechanical actuator is used to manipulate the 

accelerator pedal and allow the vehicle to accelerate and decelerate to match the desired driving 

profile. Some mileage accumulation at ETC was also conducted on emissions certification 

dynamometers when sufficient MAD capacity was not available.

During mileage accumulation, the subcontractors followed manufacturer guidelines for 

scheduled maintenance on each vehicle. Oil changes were scheduled so that they did not occur 

less than 500 miles prior to any emissions tests.

2 – DOE V4 Waiver Analysis

Battelle Memorial Institute (Battelle) acted as a data collection, dissemination, and 

analysis center for all three test sites under contract to ORNL. Battelle provided the data that 

were used in our analyses. These data included the emissions test results broken down by bag 

and calculated composite values (computed according to 40 CFR 86.144-94). These data 

included CO, NOx, and NMOG results; however, the NMOG values used for these analyses are 

estimated NMOG results that were necessary due to limitations of measurement equipment at 

two of the three labs. Part 4 of this technical memo has an in-depth discussion about the 

background and method used for the estimated NMOG calculations. 

Table 1 shows average FTP composite emissions results for NOx, CO, and estimated 

NMOG for E0 and E15 vehicles tested on the fuel the vehicle would be aged on (i.e. the vehicle 

to be aged on E15’s test results on E15) at the beginning of testing. Table 2 shows the average 

FTP composite emissions results for the end of program testing (i.e. full useful life mileage 

accumulation testing).

Table 1. Start of Testing Average FTP Composite Emissions Test Results.4

CO Nox Est. NMOG

Vehicles E0 E15 E0 E15 E0 E15

Accord 0.22 0.12 0.017 0.014 0.031 0.018

Altima 0.46 0.38 0.030 0.023 0.066 0.050

Caliber 1.02 0.66 0.035 0.030 0.054 0.046

Camry 0.15 0.15 0.019 0.039 0.019 0.032

Caravan 1.61 1.16 0.052 0.024 0.044 0.041

Civic 0.52 0.23 0.007 0.024 0.026 0.019

Cobalt 0.62 0.49 0.035 0.027 0.039 0.041

Corolla 0.42 0.33 0.021 0.019 0.034 0.032

Explorer 1.06 1.00 0.010 0.009 0.051 0.051

F150 1.42 1.42 0.038 0.030 0.046 0.065

 

4 The average differences in these results are not statistically significant (directional paired t-test, 90% confidence 

level or Sign Test) for NOx and estimated NMOG. CO results were statistically significantly lower (p=.018) for 

E15 when compared to E0 at the 90% confidence level for the paired t-test. It should be noted that these analyses do 

not take into account the differences that arise from vehicle-to-vehicle variation within a specific vehicle model. 

These analyses were not conducted for FUL test data since aging effects may impact the results.
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Focus 0.56 0.41 0.007 0.006 0.042 0.024

Impala 1.00 0.91 0.037 0.023 0.044 0.038

Liberty 0.86 0.78 0.011 0.007 0.049 0.053

Odyssey 0.23 0.18 0.009 0.010 0.021 0.025

Outlook 0.25 0.27 0.011 0.010 0.026 0.030

Quest 0.70 0.023 0.074

Silverado 0.60 0.76 0.027 0.027 0.044 0.044

Taurus 0.55 0.30 0.003 0.002 0.026 0.016

Tundra 0.69 0.88 0.020 0.029 0.048 0.072

Average 0.68 0.59 0.021 0.020 0.040 0.041

*Note: The E0 Nissan Quest data are omitted since the E0 vehicle failed to complete the test 

program

**Note: E0 and E15 results are on different vehicles, so emission differences are due to both fuel 

and vehicle differences.

Table 2. End of testing Average FTP Composite Emissions Test Results

CO Nox Est. NMOG

Vehicle E0 E15 E0 E15 E0 E15

Accord 0.23 0.13 0.026 0.024 0.048 0.018

Altima 3.18 0.62 0.067 0.053 0.135 0.055

Caliber 2.60 3.61 0.078 0.059 0.083 0.077

Camry 0.29 0.25 0.053 0.052 0.032 0.035

Caravan 1.67 1.12 0.051 0.047 0.048 0.038

Civic 0.57 0.33 0.027 0.043 0.040 0.033

Cobalt 0.87 0.47 0.042 0.027 0.039 0.039

Corolla 0.55 0.57 0.061 0.047 0.048 0.053

Explorer 1.23 1.04 0.033 0.028 0.060 0.059

F150 3.25 2.23 0.078 0.060 0.077 0.090

Focus 1.10 0.67 0.113 0.062 0.032 0.028

Impala 1.13 1.44 0.038 0.039 0.040 0.047

Liberty 0.99 1.16 0.052 0.045 0.045 0.045

Odyssey 0.60 0.20 0.074 0.039 0.051 0.028

Outlook 1.34 0.43 0.047 0.016 0.049 0.034

Quest 1.02 0.040 0.069

Silverado 0.54 0.76 0.032 0.035 0.048 0.056

Taurus 0.53 0.45 0.010 0.013 0.029 0.028

Tundra 0.80 0.94 0.042 0.035 0.052 0.055

Average 1.19 0.92 0.051 0.040 0.053 0.047

*Note: The E0 Nissan Quest data are omitted since the E0 vehicle failed to complete the test 

program

**Note: E0 and E15 results are on different vehicles, so emission differences are due to both fuel 

and vehicle differences.

The first question EPA attempts to answer when evaluating fuel waivers is whether the 

new fuel or fuel additive cause a vehicle to exceed full useful life emissions standards. With the 
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data collected from Battelle for all Tier 2 motor vehicles, the Agency compared the average 

composite emission levels for each vehicle tested on E0 and E15 to the applicable Tier 2 full 

useful life exhaust emissions standard. Based on historical analyses used to evaluate previous 

waivers, we treated these data as binomial data on whether a vehicle had passed or failed 

applicable Tier 2 full useful life standards. Vehicles that had emissions level greater than the 

applicable Tier 2 full useful life exhaust emissions standard were treated as a failure.5 We then 

conducted several analyses that are broken down into two distant types: (1) analyses that 

compare the pass/fail performance of the E0 and E15 vehicle test groups and (2) analyses that 

compared the groups independently to an “anticipated failure rate.” 

In the past, the Agency has generally performed analyses for fuel or fuel additive waiver 

requests evaluating two questions. The second question EPA looks at to evaluate a fuel waiver is 

whether the new fuel or fuel additive cause an adverse effect on the emissions of regulated 

pollutants that might contribute to vehicles exceeding their standards over their full useful life? 

For this we assessed the rate of emission deterioration of these vehicles operating on E15 in 

comparison to those operating on E10 to determine any statistically significant differences.

Further elaboration of statistical methods and results are discussed below.

Pass/Fail Analyses Comparing E0 and E15

We conducted two kinds of statistical analyses that either compared the pass/fail 

performance of the E15 vehicle test group to E0 vehicle test group or that compared the E15 and 

E0 test group separately to an anticipated failure rate.6 Table 2 shows how the Tier 2 vehicles 

that were aged on E0 performed when tested after FUL mileage accumulation relative to the 

applicable Tier 2 exhaust emissions standard while Table 3 shows how the Tier 2 vehicles 

performed on E15. 

Table 2. E0 FUL Results Compared to Tier 2 Standards

Year Model LFT@WOT Nox NMOG CO

2007 Accord N Pass Pass Pass

2006 Silverado Y Pass Pass Pass

2008 Altima N Pass Fail Pass

2008 Taurus Y Pass Pass Pass

2007 Caravan N Pass Pass Pass

2006 Cobalt N Pass Pass Pass

2007 Caliber N Fail Pass Pass

2009 Civic N Pass Pass Pass

 

5 These values assumed the applicable rounding procedures for certification as outlined in 40 CFR 86.1838-01.

6

In previous waivers, the Agency has conducted analyses that compared the failure rates of test vehicle fleets to an 

expected failure rate. 
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2009 Explorer Y Pass Pass Pass

2009 Corolla Y Pass Pass Pass

2009 Liberty N Pass Pass Pass

2005 Tundra Y Pass Pass Pass

2006 Impala Y Pass Pass Pass

2005 F150 Y Pass Pass Pass

2006 Quest N N/A N/A N/A

2009 Outlook Y Pass Pass Pass

2009 Camry Y Pass Pass Pass

2009 Focus Y Fail Pass Pass

2009 Odyssey N Pass* Pass Pass

*Denotes that average of emissions tests were below applicable FUL standard, but had at least 

one test value above the applicable FUL standard.

Table 3. E15 FUL Results Compared to Tier 2 Standards

Year Model LFT@WOT Nox NMOG CO

2007 Accord N Pass Pass Pass

2006 Silverado Y Pass Pass Pass

2008 Altima N Pass Pass Pass

2008 Taurus Y Pass Pass Pass

2007 Caravan N Pass Pass Pass

2006 Cobalt N Pass Pass Pass

2007 Caliber N Pass Pass Pass

2009 Civic N Pass Pass Pass

2009 Explorer Y Pass Pass Pass

2009 Corolla Y Pass Pass Pass

2009 Liberty N Pass Pass Pass

2005 Tundra Y Pass Pass Pass

2006 Impala Y Pass Pass Pass

2005 F150 Y Pass Pass Pass

2006 Quest N Pass Pass Pass

2009 Outlook Y Pass Pass Pass

2009 Camry Y Pass Pass Pass

2009 Focus Y Fail Pass Pass
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2009 Odyssey N Pass Pass Pass

First, the Agency compared the two groups using Fisher’s Exact Test. Fisher's exact test 

is a statistical test used to determine if there are nonrandom associations between two categorical 

variables like the pass/fail binomial data across two test groups that we are looking at in this 

program.7 Table 4 is a 2 X 2 contingency table tabulating the results of this analysis test 

program for NOx. Since the E15 vehicle test group performed similarly to the E0 test group, we 

cannot reject the hypothesis that the two vehicle test groups had different results. Since E15 

performed better for CO and estimated NMOG, the results for those pollutants are similar for 

NOx. It should also be noted that since the test subjects in this test are assumed to be 

independent, the Nissan Quest that completed testing on E15 was included in the analysis. 

However, its inclusion does not impact the results.8 Ultimately, concerning direct comparisons 

of the pass/fail performance of the E0 and E15 vehicle groups, it is unlikely that any statistical 

analysis comparing the proportion of vehicles that failed in each group would show that E15 

performed worse than E0. This is due to the fact that either fewer vehicles failed for a particular 

pollutant (e.g. NMOG and NOx) on E15 compared to E0 or that the two groups performed 

identically (e.g. CO).

Table 4. Fisher's Exact Probability Test for NOx

Pass Fail Total

E0 16 2 18

E15 18 1 19

Total 35 2 37

p= 0.374

The Agency also decided to compare the failure rate of the E15 group independently to an 

assumed “anticipated failure rate.” Vehicle testing experience has shown that various factors, 

such as testing variability and differences in vehicle performance across models lead to a small 

number of anticipated emissions failures across the national fleet. For purposes of assessment in 

this waiver, we determined our anticipated failure rate experienced in the In-use Verification 

Program (IUVP). We use this anticipated failure rate to conduct a binomial test to evaluate the 

hypothesis of whether E15 had a higher failure rate than the anticipated failure rate of 5% for 

each pollutant with a 90% confidence level. The binomial test is an exact test of the statistical 

significance of deviations from a theoretically expected distribution of observations into two 

categories (in this case pass/fail). 9 If E15 had no effect on the proportion of vehicles expected to 

fail, the number of vehicles should be approximately 5%. In this case, the low number of 

 

7

For a more formal discussion of Fischer’s Exact Test see S. Siegel, Nonparametric Statistics, New York: McGrawHill, 1956: 96.

8 With sufficient sample sizes, analyses using more continuous distributions may be used. However, given the low 

sample size in this case, it is reasonable to use Fisher’s exact test in lieu of those methods. Additionally, given the 

similar performance of the E0 and E15 vehicle test groups, it is unlikely that any such methods would demonstrate 

the E15 group performed worse than the E0 group for Tier 2 vehicles when looking strictly at whether vehicles 

passed or failed FUL certification standards.

9

For a more formal discussion of the binomial test see M. Hollander and D. Wolfe, Nonparametric Statistical 

Methods, 2

nd

, New York: Wiley-Interscience, 1999: 20.
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vehicles aged on E15 that failed to meet the emissions standards at the end of the test program 

indicates that we cannot reject the hypothesis that the rate of failure experienced in the test 

program was greater than 5% for NOx, CO, and estimated NMOG (p=0.245 for NOx, p=0.623 

for estimated NMOG, and p=0.623 for CO). Therefore, we cannot conclude that E15 caused a 

significant number of vehicles to fail meet their emissions standards when compared to the 

failure rate experienced as part of the IUVP test program.10

Emission Deterioration with E0 and E15 blends

We performed a statistical analysis of the data from the DOE catalyst durability test 

program in order to assess whether the emission deterioration rates were any different between 

the matched pairs of vehicle aged to full useful life mileage on E0 and E15 respectively. Since 

1) not all vehicles started the test program with the same mileage, and 2) deterioration over time, 

particularly at low mileage, is extremely nonlinear, it was necessary to normalize the data by 

excluding mileage points less than nominally 10,000 miles. Since the E0 Nissan Quest was not 

able to complete the program, the E15 Nissan Quest could not be included in this deterioration 

analysis. 

We chose a statistical model in the SPSSTM suite of statistical software for this analysis 

which had the following characteristics:

1) Utilized the natural logarithm of emissions,

2) Was linear in nature, 

3) Allowed each individual vehicle to have its own base emission level, 

4) Allowed each matched set of vehicles (i.e., the two F150’s) to have a unique rate of 

emissions deterioration aside from an effect of ethanol blend percentage, and

5) Allowed a single offset to the emission deterioration rate of all the vehicles to represent 

the impact of E15, in order to determine the average impact of E15 on emission 

deterioration.

The decision to analyze the natural logarithm of emissions, as opposed to emissions, was 

due to the range of base emissions observed across the test vehicles. NOx emissions at the 

lowest mileages tested varied by a factor of twelve, while NMOG emissions varied by a factor of 

four. An analysis of deterioration of absolute emissions in terms of g/mi would have placed 

great weight on those vehicles with the highest base emissions and essentially ignored those with 

the lowest emission levels. In contrast, an analysis of the natural logarithm of emissions 

essentially measures deterioration in terms of the percent of base emissions. Thus, each vehicle 

is provided roughly equal weight in this type of analysis. This approach is also consistent with 

those used in EPA’s analyses of emission data in its development of both the Complex Model 

and the EPA Predictive Models. 

The decision to utilize a linear model was necessary due to the fact that we only had 

emission data at two mileage points for a number of the test vehicles. Also, extensive experience 

with emission deterioration has demonstrated that such deterioration tends to be linear in nature 

once the catalyst is past its “green” stage and in the absence of some type of component failure. 

 

10 Using the binomial test for 19 vehicles compared to an expected probability of 0.05, two vehicles would have had 

to have failed for E15 to fail this test.
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As will be seen below, it is difficult to discern a statistically significant difference between a 

simple, linear deterioration rate. Discerning statistically significant difference between nonlinear rates would be even more difficult.

Vehicles of different model types obviously have different emission levels, as described 

above. However, even within a matched pair of vehicles of the same model type, base emissions 

vary for two reasons. One, no two vehicles’ components are exactly the same and manufacturing 

variability exists, as well. Also, the pre-owned vehicles which were part of the test program 

were driven differently prior to their purchase for the program. Thus, the degree of emission 

deterioration upon entrance into the test program were likely different. For example, eight of the 

E0-aged vehicles had lower base NMOG emissions than its matching E15-aged vehicle, while 

eight had higher base NMOG emissions.

Two, the other reason that the emissions of matched vehicles differ is the immediate 

impact of ethanol blend percentage on emissions, any effect on emission deterioration aside. 

These two effects (vehicle to vehicle and fuel) cannot be separated in this type of test program, 

since different vehicles had to be used for aging on the different ethanol blends. Thus, 

deterioration in emissions must be determined primarily using each individual vehicle’s data 

(i.e., relative to each vehicle’s baseline emission level).11 

We took a slightly different approach towards emission deterioration rate. In our 

statistical model, we allowed each group of identical vehicle models, but not each individual 

vehicle, to have its own rate of emissions deterioration. Like base emissions, individual 

vehicle’s emission deterioration rates can differ. They will differ more across vehicle type and 

model than they will between ostensibly identical vehicles (i.e., those of the same make and 

model). (In this data set, average deterioration rates can vary by an order of magnitude between 

different model types.) Still, the emissions from even identical vehicles will tend to deteriorate 

at different rates. However, we could not allow each vehicle in the modeling to have its own 

deterioration rate, as we would then have no comparison left upon which to base the effect of 

ethanol blend content on deterioration. Therefore, we essentially assumed that any differences 

in the underlying emission deterioration rate between vehicles within a model type would 

average out across the test program. The fact that all vehicles were aged using the same 

durability driving cycles during the program supports this assumption.

The net result was a statistical model with the following variables:

A coefficient for each vehicle (treating the two vehicles of the same model type as 

individual vehicles with independent coefficients)

A coefficient for each model type by the number of miles it had been aged on either E0 or 

E15 (this mileage was almost always identical for the two blends) 

A coefficient for the number of miles any vehicle had been aged on E15

This last coefficient was not vehicle specific and therefore represents the overall impact 

of E15 on emission deterioration relative to E0. Tables 2, 3, and 4 present the specific 

 

11 The instantaneous exhaust emissions impact of E15 compared to E0 is discussed in great detail in section IV.? of 

the waiver document.
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coefficients of the linear models developed for the natural logarithm of NOx, NMOG and CO 

emissions, respectively.

Table 2. Model of NOx Emission Deterioration

Base Emission Level (ln(emissions(g/mi)) Model Type 

Deterioration Rate 

(change in 

ln(emissions(g/mi)) 

per 1000 miles

Vehicle Model EO E15

2007 Honda Accord -3.978 -4.108 0.003273

2008 Nissan Altima -3.409 -3.69 0.006937

2007 Dodge Caliber -3.314 -3.674 0.009208

2009 Toyota Camry -3.769 -3.882 0.007135

2007 Dodge Caravan -3.228 -3.631 0.004621

2009 Honda Civic -3.915 -3.707 0.003623

2006 Chevrolet Cobalt -3.248 -3.827 0.004818

2009 Toyota Corolla -3.068 -3.402 0.001796

2009 Ford Explorer -3.540 -3.948 0.001839

2005 Ford F150 -3.452 -3.66 0.01195

2009 Ford Focus -3.320 -3.836 0.008952

2006 Chevrolet Impala -3.061 -3.399 -0.00308

2009 Jeep Liberty -3.943 -4.241 0.008561

2009 Honda Odyssey -3.306 -4.049 0.006325

2009 Saturn Outlook -3.749 -4.732 0.005077

2006 Chevrolet Silverado -3.566 -3.631 0.003667

2008 Ford Taurus -5.994 -5.776 0.01569

2005 Toyota Tundra -3.685 -3.704 0.006862

Change in Deterioration Rate due to E15 aging 0.00125

Table 3. Model of NMOG Emission Deterioration

Base Emission Level (ln(emissions(g/mi)) Model Type 

Deterioration Rate 

(change in 

ln(emissions(g/mi)) 

per 1000 miles

Vehicle Model EO E15

2007 Honda Accord -3.348 -3.861 0.002422

2008 Nissan Altima -2.660 -3.019 0.003436

2007 Dodge Caliber -2.946 -2.992 0.007783

2009 Toyota Camry -3.508 -3.398 0.000817

2007 Dodge Caravan -3.110 -3.233 0.001839

2009 Honda Civic -3.451 -3.604 0.001919
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2006 Chevrolet Cobalt -3.340 -3.166 0.000669

2009 Toyota Corolla -2.837 -2.548 -0.00172

2009 Ford Explorer -3.106 -2.979 0.002885

2005 Ford F150 -3.004 -2.799 0.007143

2009 Ford Focus -3.510 -3.305 -0.00129

2006 Chevrolet Impala -3.229 -3.194 0.000973

2009 Jeep Liberty -2.851 -2.533 -0.00299

2009 Honda Odyssey -3.478 -3.85 0.0034

2009 Saturn Outlook -3.115 -3.332 0.000658

2006 Chevrolet Silverado 0.082 -3.058 0.003436

2008 Ford Taurus -3.825 -3.996 0.002629

2005 Toyota Tundra -3.095 -2.898 0.002404

Change in Deterioration Rate due to E15 aging -0.00114

Table 4. Model of CO Emission Deterioration

Base Emission Level (ln(emissions(g/mi)) Model Type 

Deterioration Rate 

(change in 

ln(emissions(g/mi)) 

per 1000 miles

Vehicle Model EO E15

2007 Honda Accord -3.377 -3.99 0.002451

2008 Nissan Altima -2.689 -3.163 0.003453

2007 Dodge Caliber -2.979 -3.133 0.007827

2009 Toyota Camry -3.531 -3.539 0.00077

2007 Dodge Caravan -3.140 -3.373 0.001829

2009 Honda Civic -3.471 -3.741 0.001832

2006 Chevrolet Cobalt -3.367 -3.303 0.000645

2009 Toyota Corolla -2.868 -2.69 -0.00175

2009 Ford Explorer -3.126 -3.114 0.002829

2005 Ford F150 -3.032 -2.937 0.007082

2009 Ford Focus -3.545 -3.456 -0.00117

2006 Chevrolet Impala -3.256 -3.337 0.000987

2009 Jeep Liberty -2.879 -2.667 -0.00306

2009 Honda Odyssey -3.511 -4.001 0.003464

2009 Saturn Outlook -3.147 -3.481 0.000698

2006 Chevrolet Silverado 0.081 -3.197 0.00343

2008 Ford Taurus -3.856 -4.12 0.002521

2005 Toyota Tundra -3.123 -3.036 0.002376

Change in Deterioration Rate due to E15 aging -0.00109
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Table 5 summarizes the average emission deterioration rates on the E0 and E15 blends. 

The average emission deterioration rate for the E0 blend is the average of the vehicle specific 

deterioration rates shown in Tables 2, 3, and 4 above, respectively, for NOx, NMOG and CO 

emissions. The average emission deterioration rate for the E15 blend is the average deterioration 

rate for the E0 blend plus the change in deterioration rate to due to E15 aging shown in these 

same tables.

Table 2. Emission Deterioration on E0 and E15 Blends (ln(emissions per 1000 miles)

NOx NMOG CO

E0 deterioration rate 0.0060 0.0020 0.0020

E15 deterioration rate 0.0072 0.0009 0.0009

The results of the statistical analysis shown in Table 5 indicate that the rate of 

deterioration in NMOG and CO emissions decreased slightly on average, while that for NOx 

emissions increased slightly. However, none of the three impacts were statistically significant 

deterioration at the 90% confidence level.12 Thus, due to the variability in the effect across the 

various test vehicles, we cannot confidently reject the hypothesis that the emission deterioration 

rates on both blends are the same. In other words, there is a significant chance that the average 

impacts observed are the result of the randomness in the data. This conclusion is supported by

the fact that the average changes in NMOG/CO and NOx emission deterioration rates went in 

opposite directions. If the catalysts had in fact been deteriorating faster with E15, then all 

emissions should have deteriorated consistently. Therefore, the catalyst durability test program 

results also support the conclusion that E15 will not contribute to Tier 2 vehicles exceeding their 

emission standards over their full useful life.

3 – Analysis of SwRI Powertrain Component Inspection Data 

Background

Southwest Research Institute released a report , (SwRI®) Project 08-58845 Status Report, 

"Powertrain Component Inspection from Mid-Level Blends Vehicle Aging Study”, that details 

the results of their Teardown measurements of the engines from the vehicles that they aged as 

part of the DOE Catalyst Durability Program. 

Summary

Six pairs of engines and fuel system components were disassembled and analyzed for signs of 

wear and material compatibility problems after E0 and E15 mileage accumulation. Vehicles 

were matched pairs of used vehicles from MY2006 to MY2008 with mileage ranging from 10k 

 

12 The Agency has typically used a confidence level of 90% in CAA section 211(f)(4) waiver requests instead of the 

more conventional 95% confidence level. We feel that the 90% confidence level increases the likelihood that 

increases in deterioration would be statistically significant and therefore would be more conservative in this case. 

However, these differences are also not statistically significant at the 95% confidence level.
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to 50k miles prior to the program. Miles of test program aging ranged from 68K to 102K miles 

depending on the initial mileage. 

The following powertrain components were analyzed:

 evaporative system for leaks

 evaporative canister working storage capacity

 intake valve deposits

 valves and camshafts for wear

 fuel pump flow performance

 Fuel injector flow rate analysis

 Engine oil chemical analysis for wear particles

 Intake valve seals were visually inspected.

Making any conclusive statements about the inspection data is limited by the lack of baseline, 

“before”, measurements prior to the aging program’s start, and the aging process itself. So it is 

not the most rigorous for engine components and materials. Furthermore, the engines were run 

near continuously with few starts or soaks. Nevertheless, It would only be noteworthy if 

significant component degradation did occur. 

Nonetheless, looking at the following observations, the measurement results show no systemic 

trends pointing to greater wear or degradation caused by fuel-related differences. The one very

consistent trend was a greater buildup of valve deposits with E15 use –possibly due to detergent 

dilution when displacing 15% of the gasoline with Ethanol. 

Types of analysis performed

Evaporative Emissions System Integrity Check—Evaporative system leak checked using a 

pressure test and smoke. All vehicles passed the tests. 

Evaporative Canister Butane Working Capacity– Measure each canister’s working storage 

capacity (maximum amount of fuel vapor that can be absorbed). With no measurements taken 

before aging, we can only make relative comparisons between the canisters from E0 aged 

vehicles to canisters from matching E15 aged vehicles. When comparing the 6 Canisters aged 

on E15 to the matching 6 aged on E0, there was no trend indicating any difference between 

them. The variations in results was uniformly distributed. No statistically significant change in 

evaporative canister working capacity is suggested with this small data set.

Intake Valve Deposits - Quantified in milligrams by weighing the valves before and after 

cleaning them. All of the E15 engines have a consistent and often very significant increase in 

intake valve deposits. 41 of the 44 (95%) intake valves from E15 aged engines had more 

deposits than the valves from the E0 aged engines. 77% of the E15 valves had more than twice 

the deposits as their corresponding E0 valves. This could be the result of having 15% less 

detergent in the fuel as the Ethanol displaced the detergent-enriched gasoline. 

Valvetrain / Camshaft Measurements-- The following measurements (cam lobe, valve seat 

and valve stem height) are intended to check if there is any noticeable increase in wear on the 
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camshafts and valve seats due to the E15 fuel usage. Only limited observations are possible 

from the data since there were no baseline “before” measurements prior to the aging program’s 

start. Nonetheless, looking at the observations following below, the measurement results show 

no systemic trends pointing to greater wear caused by the E15 exposure. 

Cam Lobe Wear- The overall cam lobe height was measured for any indications of increased 

wear with E15 fuel compared to the E0 aging. As stated in the SWRI report, “Because the cams 

were not measured at the beginning of the program, and due to normal part-to-part variation, 

the measurements are potentially inconclusive with respect to any fuel-related differences in cam 

wear”. With no “before” measurements, there are no actual wear numbers to compare. 

Nonetheless, by comparing the final lobe dimensions of the 12 pairs of camshafts (intake plus 

exhaust) there are two observations. 

 There is no trend showing smaller E15 lobes. Looking at each matched pair, only 2 of 

the 12 E15 aged camshafts have smaller dimensions than the corresponding E0 cam. 

 The typical differences were less than 0.02mm (0.0008”). This is very minimal and may 

be due more to the variation of the initial cam grinding process than wear. 

Valve Seat Width and Valve Surface Contour – 3 different dimensions were measured on the 

valve seat surface for indications of valve seat recession. Without initial measurements, results 

aren’t conclusive since we don’t know how much wear was due to the aging program versus 

prior aging on unknown fuels.

 

With that limitation in mind and focusing the peak wear depth on the valve seat contact point 

(the report labeled this the “Z” term): 

 Comparing the matched sets of valves, all E15 engines showed similar or less wear than 

their corresponding E0 valves, except for the Silverado.

 Intake valve seat wear for both E0 and E15 aged engines was 1 to 8 microns or, more 

importantly, less than 0.0001”. 

 Exhaust valve seat wear was typically 8 to 25 microns with the Silverado approaching 30 

microns (0.0012”). It is normal for Exhaust valves to wear more than intake valves. 

 Such low wear values indicate none of the valves experienced significant wear on this 

the particular aging cycle. Field vehicles with high mileage can have more than ten 

times this amount of wear. 

Valve Stem Height - valve stem height increase can be an indicator of valve seat recession. 

Unfortunately, it is variable with casting and machining variances. 

As stated in the SWRI report: “Because valve stem heights at the beginning of the program are 

not known, and because of variations in actual cylinder head geometry and valve length, it is 

difficult to draw any conclusions about valve seat wear.”

 There is no consistent difference between the E0 and E15 engines when comparing valve 

heights between corresponding pairs of engines. 

 The exception is the Accord exhaust valves which are uniformly taller on the E0 engine. 

This is likely a manufacturing difference. 

 Several E15 engines had 1 valve noticeably taller than the rest. There is no way to 

determine if this is manufacturing variability or valve recession. 
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ASTM D5185 Analyses of Engine Oil Drain Samples –

The difference in metal levels between the E0 and E15 related oil samples do not show any

trends indicating that E15 increases internal engine wear relative to E0 fuel.

As stated in the SWRI report: “There do not appear to be any unusually high wear metal levels 

in any of the engine oil drains.” 

Fuel Pump Evaluations - Fuel pump flow rate was measured at pressures above and below the 

mean expected pressure specified by the manufacturerSome pumps exhibited different flow rates 

but without measurements before the start of aging, we can not distinguish between part-to-part 

variation and deterioration. None of the flow rate curves looked significantly different between 

the two aging fuels in the matched pairs.

As stated in the SWRI report: “While pump characteristics prior to the vehicle aging program 

are unknown, there do not appear to be any serious differences between the RE0 fuel pumps and 

the RE15 fuel pumps.” 

Fuel Injector flow rate analysis- SwRI flow tested the injectors at 3 duty cycle settings. They

concluded all injectors fall within 3% of the mean for each engine application. It appears these 

were static flow tests which are less sensitive to pintle characteristics. Dynamic testing would be 

more appropriate for detecting any pintle mechanical degradation. While the test results 

indicate no adverse effects related to ethanol exposure, a more appropriate measurement would 

allow a definitive conclusion. 

4 – Estimated NMOG Calculation

The term “non-methane organic gases” (NMOG) describes the sum of hydrocarbon 

emissions other than methane that may or may not contain oxygen, a set that is inclusive of many

compounds that are both directly harmful to health as well as contribute to smog and ozone 

pollution. Oxygen-containing species (referred to as oxygenated hydrocarbons, or OHCs) are 

typically a very small fraction of NMOG emissions for non-oxygenated fuels, but can become a 

significant portion for a gasoline-ethanol blended fuel. As such, NMOG is the basis for Tier 2 

emissions standards, and also for evaluating emissions related to the waiver decision.

Generation of NMOG results from an emission test is complicated by the fact that the 

type of hydrocarbon analyzer typically used in emission test cells produces an incomplete 

account of OHCs. Thus, the OHCs must be measured by other methods and combined with the 

non-methane hydrocarbon (NMHC or NONMHC) to properly account for all NMOG emissions.

During the planning phase of the program, EPA and DOE staff agreed that NMOG 

emissions would be computed as NONMHC plus at least methanol, ethanol, formaldehyde, and 

acetaldehyde. Other alcohol and/or carbonyl species may be included, but typically don’t change 

the result significantly since they are emitted in much smaller amounts than these. 
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As described in Section 1 above, DOE used three commercial emission testing companies 

to produce emission results for this waiver: Southwest Research Institute (SwRI), Transportation 

Research Corporation (TRC), and Environmental Testing Corporation (ETC). Between the three 

labs, there were differences in both how OHCs were measured and how NMOG was calculated, 

complicating the task of aggregating all results into a consistent form necessary for evaluation of 

the data. Of the three labs, SwRI measured the required OHCs for all tests, in a way consistent 

with typical best practices, and computed NMOG accordingly. ETC did not produce useable 

OHC results for all compounds for all tests, and thus were not able to compute NMOG as 

defined for all tests due to the level of uncertainty in the emission measurement. TRC utilized an 

approach similar to ETC at the start of testing, but then switched part-way through the test 

program to measure OHC emissions similar to SwRI.

Due to the inconsistencies in data, DOE (in agreement with EPA) performed calculations 

on the contractor-reported values to produce NMOG estimates for all tests on a consistent basis. 

The first step was to produce NONMHC from test-cell-reported values (that contained 

incomplete accounting for oxygenated species) for all 3 laboratories that were all measured on a 

consistent basis. Attached to this memo is a document entitled “Derivation of Mass-Correction 

Method for NMOG Determination, August 20, 2010” that describes this calculation in detail.

The second step was to adjust the NONMHC results to reflect the presence of OHCs in 

NMOG emissions. Examining data from SwRI, the NMOG to NONMHC ratio was found to 

have a linear correlation with fuel ethanol content. A linear fit equation was generated for this 

ratio as a function of fuel ethanol content for composite (FTP weighted) emission results. This 

equation is given here, solved for NMOG, where ETOH is defined as the fuel ethanol content in 

volume percent:

estimated NMOG  NONMHC 1.0293  0.0079 ETOH

To avoid inconsistent treatment of vehicles and fuels between the three labs, this equation 

was used to generate estimated NMOG results for all tests in the program. This approach is 

sufficiently accurate to address the question of whether a vehicle’s emissions deterioration is 

worse with E15, since this question involves looking at rates of change, and tests at all mileage 

points are consistently treated by the ratio. We believe it is also sufficiently accurate to estimate 

actual NMOG measurements, as the difference between estimated and actual NMOG 

measurements, where data was available, is very small.