UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY

2000 TRAVERWOOD DRIVE

ANN ARBOR, MI 48105-2498

 OFFICE OF

AIR AND RADIATION

March 1, 2013

MEMORANDUM

SUBJECT: Test Program to establish LDV Full Useful Life PM Performance

FROM: Rafal Sobotowski – USEPA/OTAQ/ASD

TO: EPA Docket # EPA-HQ-OAR-2011-0135

Description of the Full Useful Life Program

In order to establish the feasibility of the particulate matter (PM) emission

standards proposed in the Tier 3 rule, the U.S. EPA conducted a test program to measure

PM emissions from Tier 2 light-duty vehicles. The test program was designed to 

measure PM emissions from late model year vehicles that represented a significant 

volume of annual light duty sales and included vehicles that ranged from small cars 

through trucks, including a cross section of technologies from port fuel injected (PFI)

engines to gasoline direct injection (GDI) engines. In addition, one PFI vehicle was

included with known high oil consumption.

Seventeen model year 2005-2010 Tier 2 Bin 4, 5, and 8 vehicles were tested at the 

U.S. EPA National Vehicle and Fuel Emissions Laboratory (NVFEL) facility. A 

summary of their characteristics is provided in Table 1. They included ten cars and seven 

trucks. Fifteen of these vehicles had accumulated 102,000-124,000 miles prior to the 

launch of the test program. One vehicle had accumulated 37,000 miles and another 

accumulated 21,000 miles. Three cars and one truck were equipped with Gasoline Direct 

Injection (GDI) engines. Twelve of the seventeen test vehicles had previously been used 

in the Department of Energy (DOE) V4 Program. The remaining five vehicles were 

recruited in southeastern Michigan. 

The twelve vehicles acquired from the DOE V4 Program were selected to 

represent a broad cross section of some of the highest sales vehicles in the U.S. market 

for model years 2005-2009. These vehicles had originally been purchased by DOE with 

odometer readings ranging from 10,000-60,000 miles, placed in a mileage accumulation 
program and operated over the EPA Standard Road Cycle on a test track or on mileage 

accumulation dynamometers to 110,000-120,000 miles.iImmediately prior to inclusion 

in the EPA PM Test Program, the test vehicles were serviced per the manufacturer’s 

published service schedule and maintenance procedures and underwent engine oil aging 

over a distance of 1,000 miles accumulated over the EPA Standard Road Cycle to 

stabilize engine oil contribution to PM emissionsii.

One vehicle (vehicle K) tested from the DOE V4 program was suspected of 

having atypically high oil consumption and had only 37,000 miles of mileage 

accumulation. Vehicle K was a duplicate of Vehicle C and was determined to consume 

two and one half times the average oil consumption of vehicle C and three vehicles of the 

same make, model and model year which were tested within the DOE V4 program.1

Vehicle K did not accumulate 120,000 miles because it was removed from the mileage 

accumulation program after the atypical oil consumption was confirmed. Vehicle K was 

tested in this program to investigate the potential impact of high oil consumption on PM 

emissions. Three recruited test vehicles were selected because they used GDI technology

and one GDI equipped vehicle was obtained from the DOE V4 Program. Vehicle Q was 

recruited for another test program but was included in this program because it was a GDI 

technology vehicle. Otherwise, an attempt was made to only recruit vehicles approaching 

the 120,000 mile useful life level. All of the recruited test vehicles were thoroughly 

inspected, but otherwise tested as received.

All vehicles were tested on an E15 fuel with RVP, aromatic content, sulfur 

content, T50 and T90 of 9.1 psi, 23.8 vol%, 7 ppm, 160F and 311F, respectively. The 

properties of this fuel approximated those of a projected E15 market fuel.

The test program included three cold start and three hot start UDDS tests and 

three US06 tests conducted on each vehicle. FTP results were calculated for gaseous and 

PM emissions by applying the cold-start and hot-start weighting factors to the complete 

cold and hot UDDS results, respectively. This eliminated separate analysis of the 

typically very low concentration FTP phase-2 gaseous and PM emissions samples and 

represented one method proposed within 40 CFR 1066 for increasing sample integration 

of measured gaseous and PM mass. During these tests, triplicate PM samples were 

collected in parallel on PTFE membranes and single (composite) PM samples were 

collected on primary and secondary quartz filters for Thermol Optical Reflectance (TOR) 

Organic Carbon (OC) and Elemental Carbon (EC) PM speciation analysis. Additional 

quartz filters were collected to determine the contribution of gas-phase artifact to the OC 

collected on the quartz filter samples. The compositing of quartz filters over three 

repeats of each test was done to enhance the precision of subsequent OC/EC 

thermogravimetric measurements. Single background (dilution air) PM samples were 

also taken during each emissions test. Weekly tunnel blank and field blank PM samples 

were also collected. 

 

1 Vehicle K consumed approximately 1 quart per 3,000 miles vs. an average of approximately 1 quart per 

8,000 miles for the other four vehicles of this make, model and year tested within the DOE V4 program.
The following parameters were measured: NOX, NMHC, NMOG, alcohols, 

carbonyls, CO, CH4, CO2 and fuel consumption and PM mass as per the 40 CFR 1065 

and the proposed 40 CFR part 1066 test procedures. Limited exhaust HC speciation was 

also performed.

PM composition was determined from filter samples taken on both quartz filters 

and PTFE membranes. PM compositional analyses include determination of the 

contribution of elemental and organic carbon to PM mass,iii elemental analysis via energy

dispersive x-ray fluorescence (EDXRF), and sulfate analysis via ion chromatography. 

Table 1. Vehicles tested as part of EPA’s Light-Duty Vehicle PM Test Program 

Vehicle Make, Model 

and Designation

Model 

Year

Certified to 

Emissions 

Standard

Odometer at 

Start of 

Program, miles

Fuel 

Deliverya

Used in 

DOE V4 

Program?

Honda Civic A 2009 Tier 2/Bin 5 121,329 PFI Yes

Toyota Corolla B 2009 Tier 2/Bin 5 120,929 PFI Yes

Honda Accord C 2007 Tier 2/Bin 5 123,695 PFI Yes

Dodge Caliber D 2007 Tier 2/Bin 5 114,706 PFI Yes

Chevrolet Impala E 2006 Tier 2/Bin 5 114,284 PFI Yes

Ford Taurus F 2008 Tier 2/Bin 5 115,444 PFI Yes

Toyota Tundra G 2005 Tier 2/Bin 5 121,243 PFI Yes

Chrysler Caravan H 2007 Tier 2/Bin 5 116,742 PFI Yes

Jeep Liberty I 2009 Tier 2/Bin 5 121,590 PFI Yes

Ford Explorer J 2009 Tier 2/Bin 4 121,901 PFI Yes

Honda Accord K 2007 Tier 2/Bin 5 36,958 PFI Yes

Ford F150 L 2005 Tier 2/Bin 8 111,962 PFI No

VW Passat M 2006 Tier 2/Bin 5 102,886 TGDI No

Chevrolet 

Silverado P 2006 Tier 2/Bin 8 110,898 PFI No

Manufacturer’s 

Development 

Vehicleb

N PC

None (Tier 

2/LEV II 

Prototype)*

120,011 TGDI No

Saturn Outlook O 2009 Tier 2/Bin 5 123,337 GDI Yes

Cadillac STS4 Q 2010 Tier 2/Bin 5 21,266 GDI No

Notes:

a

PFI is Naturally aspirated, port fuel injected; GDI is Naturally aspirated, gasoline direct 

injection; TGDI is Turbocharged, gasoline direct injection

b Manufacturer’s developmental vehicle. Vehicle used a spray-guided GDI fuel system 

with a centrally-mounted injector and turbocharging. Emissions were targeted at Tier 2 

Bin 5 or better. 
Original Particulate Matter Results (Fall 2011)

The original particulate matter test results measured in this program are plotted in 

Figure 1 and Figure 2, for the FTP and US06 test cycles, respectively. In the figures, the 

vehicles are divided into two groups: PFI and GDI. Within each group they are listed in 

the sequence of increasing CO2 emissions on the FTP test cycle. The colored bars shown 

in the figures represent the means by test cycle and vehicle, and include accompanying 

standard deviations. The data points indicate the average emissions for each individual 

vehicle test. The number of tests, mean PM emission rates, and standard deviations by

vehicle are tabulated in Tables 2 and 3. All reported tests passed the Federal Register 

proportionality requirements for particulate sampling light-duty gasoline exhaustiv.

Vehicles I and M are not included in Figure 3 because the tests did not meet the 

proportionality requirements on the FTP cycle. 

As shown, the original PM emission rates for PFI vehicles were quite low on the 

FTP cycle, but were very high on the US06 for several PFI vehicles. The original results 

on the US06 showed that several of the PFI vehicles had very high PM emission rates, 

which tended to be the higher-weight trucks. 

Figure 1. Original composite FTP PM emission results. Individual test results are 

marked with data points, average test results by vehicle ± 1 standard deviation are 

displayed with the bar graphs. 

F

T

P

P

M (m

g/mile)

0

2

4

6

8

10

PFI (PC)

PC

A B C K D E F

PFI (LDT1/2)

LDT1/2

G H

PFI (LDT3/4)

LDT3/4

P J L

GDI

PC PC LDT3/4

N Q O
Figure 2. Original US06 PM emission results. Individual test results are marked with 

data points, average test results by vehicle ± 1 standard deviation are displayed with the 

bar graphs. 

PM Sampling Contamination Issue

Upon review of the elemental analysis results, high concentrations of silicon (Si) 

were discovered on some of the PTFE filters. Corresponding Si emission rates in mg/mile 

are reported in Tables 2 and 3, and displayed in Figure 3 and 4 for the FTP and US06 

cycles. The highest Si emission rates were all measured on the US06 cycle, and were 

more than an order of magnitude higher than the highest Si emission rate reported on the 

FTP cycle. The Si emission rates on the US06 exhibited substantial variability, spanning 

four orders of magnitude among the different vehicles. The highest Si emission rates 

occurred predominately on the trucks. Each of the vehicles with high Si emission rates 

also had high PM emission rates on the US06. 

U

S

0

6

P

M (m

g/mile)

0

10

20

30

40

50

PFI (PC)

PC

A B C K D E F

PFI (LDT1/2)

LDT1/2

G H I

PFI (LDT3/4)

LDT3/4

P J L

GDI

PC PC LDT3/4

N Q O
Table 2. Original FUL FTP composite PM and Si results by vehicle

Vehicle Tests

PM mean 

(mg/mi)

PM sd 

(mg/mi)

Si mean 

(ug/mi)

Si sd 

(ug/mi)

A 3 0.27 0.11 9.5 2.8

B 3 0.22 0.09 5.1 3.5

C 3 0.18 0.07 5.6 1.4

K 3 0.93 0.23 3.6 0.7

D 3 0.45 0.10 11.4 0.8

E 3 0.14 0.03 2.9 1.3

F 3 0.11 0.06 4.8 1.3

G 3 0.36 0.05 11.6 3.6

H 3 0.40 0.22 13.8 4.9

I - - - - -

P 3 1.22 0.12 22.0 2.5

J 3 0.11 0.10 10.2 5.8

L 3 0.81 0.14 16.8 5.6

N 3 2.55 0.74 47.9 4.2

M - - - - -

O 2 4.72 0.30 84.6 3.5

Q 1 7.15 - 73.0 -

Table 3. Original FUL US06 Composite PM and Si results by vehicle

Vehicle Tests

PM mean 

(mg/mi)

PM sd 

(mg/mi)

Si mean 

(ug/mi)

Si sd 

(ug/mi)

A 2 0.76 0.35 18.4 0.2

B 3 2.05 0.41 225.6 61.9

C 3 1.05 0.36 101.5 36.4

K 3 2.84 1.08 257.5 128.7

D 3 7.39 3.16 1447.5 605.0

E 3 0.46 0.36 10.1 7.4

F 3 1.61 0.09 243.6 5.8

G 2 5.84 1.10 866.7 350.2

H 3 2.04 0.64 295.0 84.6

I 2 24.44 19.26 4349.7 3939.1

P 3 29.46 2.10 4777.3 1119.4

J 3 41.93 5.97 7441.1 1038.2

L 3 8.82 1.21 1298.3 18.5

N 3 2.37 0.25 133.1 19.1

M 3 37.42 18.59 516.8 250.3

O 3 4.75 1.03 858.4 247.7

Q 3 11.13 5.98 629.9 374.2
Figure 3. Original composite FTP silicon emission results. Individual test results are 

marked with data points, average test results by vehicle ± 1 standard deviation are 

displayed with the bar graphs. 

Figure 4. Original composite US06 silicon emission results. Individual test results are 

marked with data points, average test results by vehicle ± 1 standard deviation are 

displayed with the bar graphs. 

Sources of contamination were investigated in the test cell used for this program 

at the NVFEL facility. The investigation discovered that silicone elastomer transfer tubes 

(pictured in Figure 5) were used to transfer the tailpipe exhaust from the vehicle to the 

constant volume sampler (CVS) system. Silicone is a polymer that contains Si, C, H, and 

O atoms, which can break down at high temperature and exposure to lubricating oilv. The 

silicone tubes were suspected as the source of the high measured Si and PM rates on the 

US06. Maricq et al. (1999) confirmed that silicone couplers can contribute to high 

concentrations of ultrafine particles measured under high exhaust temperaturesvi.

F

T

P

Silicon E

missions (m

g/mile) 0.00

0.02

0.04

0.06

0.08

0.10

PFI (PC)

PC

A B C K D E F

PFI (LDT1/2)

LDT1/2

G H

PFI (LDT3/4)

LDT3/4

P J L

GDI

PC PC LDT3/4

N Q O

U

S

0

6

Silicon E

missions (m

g/mile)

0

2

4

6

8

10

PFI (PC)

PC

A B C K D E F

PFI (LDT1/2)

LDT1/2

G H I

PFI (LDT3/4)

LDT3/4

P J L

GDI

PC PC LDT3/4

N Q O
Figure 5. Silicone exhaust transfer tubes used in initial NVFEL testing

A follow-up investigation program was conducted to verify the effect of silicone 

sampling lines on PM emissions and to assess its magnitude on the PM emission rates. 

Vehicle J (Ford Explorer) was selected for the investigation follow-up test program 

because it was the vehicle with the highest recorded PM and Si emission rates on the 

US06 test cycle. Three US06 tests were conducted with the silicone rubber transfer lines, 

and three tests with stainless steel transfer lines. Figure 6 graphs the PM emission rates 

recorded from the 2009 Ford Explorer. The average PM emission rates were 10.28 

mg/mile with the silicone transfer tube and 0.92 mg/mi with the stainless steel transfer 

line. The Si emission rates with the silicone transfer tube were on average 0.91 mg/mile, 

but were only 0.003 mg/mile with the stainless steel transfer line. Using the results from 

the follow-up Ford Explorer US06 tests, almost all the PM measured on the US06 was 

coming from the silicone transfer tube. As suspected, the measured elemental silicon was 

only a portion of the silicone break down products that contributed to the particulate mass 

on the PTFE filter samples. In the case of the follow-up investigation, the elemental Si 

only contributed ~ 10% of the increase in measured PM. The follow-up study confirmed 

that silicone elastomer exhaust connections exposed as wetted surface area to hot engine 

exhaust can contribute substantially to particulate matter filter sample mass from CVS 

samples. 
Figure 6. US06 PM results from follow-up investigation on silicone elastomer

transfer tubes

Criteria for Test Removal

The follow-up investigation demonstrated that samples contaminated excessively

by silicone transfer lines were no longer valid and need to be excluded. The elemental Si 

emission rates were used to identify tests with excessive silicone contamination. The 

follow-up test program estimated that silicone lines can contribute up to 10 times as much 

PM as measured elemental Si, yielding a PM:Si ratio of 10. The PM:Si ratio likely varies 

test-to-test and vehicle-to-vehicle, and the PM:Si ratio for most tests appears to be 

smaller than 10. By applying a 10:1 PM:Si ratio to the US06 Si data in Table 3, the 

silicone transfer tube would contribute more PM than was measured for nine of the 

sixteen vehicles, including Vehicle J (Ford Explorer). 

All vehicles that had elemental Si emission rates greater than 300 μg/mi (0.3 

mg/mi) were excluded. This limit was selected to assure that none of the high PM 

emission rates on the US06 were caused by silicone contamination. This criteria 

excluded eight vehicle tests on the US06: one PFI car (Vehicle D), five PFI trucks 

(Vehicle G, I, P, J, L) and two of the GDI vehicles (Vehicle Q, O). Using this criterion, 

the silicone transfer tube cannot contribute more than 2.84 mg/mile in the any of the 

remaining US06 PM averages, because all the remaining US06 PM values are less than 

2.84 mg/mi (Vehicle K), notwithstanding the remaining Si rates are below 300 μg/mi. 

The FTP tests had minor contributions of silicone contamination compared to the 

US06 cycle. This is expected due to the smaller engine loads and lower exhausts 

0

2

4

6

8

10

12

14

PM (mg/mi)

US06 PM Emission Rates from 2009 Ford Explorer 

Silicone Transfer Tube

Stainless Steel
temperatures experienced on the FTP cycle. None of the FTP composite emission rates 

had Si emission rates above 100 μg/mile. Assuming the 10:1 PM to Si ratio is an upper 

bound, the maximum silicone PM contribution on the final FTP results were 0.84

mg/mile, using the maximum FTP Si emissions recorded from Vehicle O. 

Supplemental Test Program (Summer 2012)

The light-duty trucks with the four highest US06 PM and Si rates (J, I, L, and P) 

were retested at the NVFEL laboratory with stainless steel exhaust transfer lines on the 

same test fuel as the original test program. The results for both the FTP and US06 from 

the stainless steel tests were used to replace the original data. 

The final set of PM results (which includes all the retests) is graphed in Figure 7 

and Figure 8 for the FTP and US06 test cycles, respectively. The final average PM 

emission rates, number of tests and standard deviations are presented in Table 4. The 

quality control criteria of 300 μg/mile appears to be a reasonable cutoff for excluding 

vehicle tests from the sample for demonstrating compliance. Vehicle I had the highest

PM emission rates in the final US06 data set which was tested with the stainless steel 

transfer line. The US06 cycle PM emission rates from four vehicles (D, G, M and O)

were removed due to silicone contamination and were not retested. The FTP results from 

three of these vehicles are reported. The FTP results from Vehicle M were removed due 

to proportionality requirements as discussed earlier.

Figure 7. Final composite FTP PM emission results. Individual test results are marked 

with data points, average test results by vehicle ± 1 standard deviation are displayed with 

the bar graphs. 

F

T

P

P

M (m

g/mile) 0

2

4

6

8

PFI (PC)

PC

A B C K D E F

PFI (LDT2)

LDT2

G H I

PFI (LDT3/4)

LDT3/4

P J L

GDI

PC PC LDT3

N Q O
Figure 8. Final US06 PM emission results. Individual test results are marked with data 

points, average test results by vehicle ± 1 standard deviation are displayed with the bar 

graphs. 

Table 4. Final PM results for the composite FTP and the US06

Composite FTP US06

Vehicle n Mean (mg/mi) SD (mg/mi) n Mean (mg/mi) SD (mg/mi)

A 3 0.27 0.11 2 0.76 0.35

B 3 0.22 0.09 3 2.05 0.41

C 3 0.18 0.07 3 1.05 0.36

K 3 0.93 0.23 3 2.84 1.08

D 3 0.45 0.10 Removed

E 3 0.14 0.03 3 0.46 0.36

F 3 0.11 0.06 3 1.61 0.09

G 3 0.36 0.05 Removed 

H 3 0.40 0.22 3 2.04 0.64

I

1

2 1.36 0.08 2 3.31 0.81

P

1

3 0.18 0.06 3 1.83 0.81

J

1

3 0.10 0.04 3 0.27 0.01

L

1

3 0.39 0.13 3 2.13 1.76

N 3 2.55 0.74 3 2.37 0.25

O 2 4.72 0.30 Removed

Q 1 7.15 - Removed

Notes:

1Retested vehicles at NVFEL laboratory with stainless steel 

U

S

0

6

P

M (m

g/mile) 0

2

4

6

8

PFI (PC)

PC

A B C K E F

PFI (LDT2)

LDT2

H I

PFI (LDT3/4)

LDT3/4

P J L

GDI

PC

N
Discussion

The silicone contamination issue had a very significant impact on the results of 

the US06 cycle, illustrated most dramatically with Vehicle J, which reduced the US06 

PM emissions from over 40 mg/mile with the silicone contamination to under 1 mg/mile 

with the stainless steel transfer line. The silicone contamination on the FTP cycle was 

minor and no tests were removed or replaced due to silicone contamination. 

In the final data set, all but one of the PFI vehicles had FTP PM emission rates 

under 1 mg/mile, and all PFI vehicles had emissions below the proposed 3 mg/mi FTP 

standard. On the US06 cycle all of the PFI vehicles were well in compliance of the 

proposed US06 standards, and all tests were below 4 mg/mile. 

The GDI vehicles all had higher FTP emissions than the highest tested PFI 

vehicle. In comparison to the proposed 3 mg/mi standard, only Vehicle N, the sprayguided OEM vehicle, had average FTP emissions below the standard. More testing on 

GDI vehicles is needed to evaluate their PM emissions on the US06 cycle, but the current 

testing shows that GDI technology (Vehicle N) can perform comparable to PFI engine

technology on the US06 cycle. 

 

i U.S. Code of Federal Regulations, Title 40, § 86.1823–08 Durability demonstration procedures for 

exhaust emissions.

ii Christianson, Michael G. “Impact of Lubricating Oil Condition on Exhaust Particulate Matter Emissions 

from Light Duty Vehicles” SAE Technical Paper No. 2010-01-1560

iii Chow, J.C.; Watson, J.G.; Crow, D.; Lowenthal, D.H.; Merrifield, T. Comparison of IMPROVE and 

NIOSH Carbon Measurements. Aerosol Sci.Technol., 2001, 34, 23-34.1.

iv U.S. Code of Federal Regulations, Title 40, § 86.1310-2007 Exhaust gas sampling and analytical system 

for gaseous emissions from heavy-duty diesel-fueled engines and particulate emissions from all engines.

v Keller, R. W.; Effects of Engine Oils on Silicone Oil Seal Material. SAE Technical Paper Series 860494. 

1986.

vi Maricq, M. Matti., Chase, Richard E. Podsiadlik, Diane H.; Vehicle exhaust particle size distributions: A 

comparison of tailpipe and dilution tunnel measurements. SAE Paper 1999-01-1461