1

INDUSTRY LOW-SULFUR

TEST PROGRAM

• AUTOMOBILE-INDUSTRY LEV/ULEV 

VEHICLE TEST PROGRAM 

(The Alliance, AIAM and Honda)

• PERFORMED AT REQUEST OF CARB 

IN CONJUNCTION WITH MTBE-BAN 

AND NEW CBF3 REGULATIONS

• PERFORMED WITH COOPERATIVE 

ASSISTANCE OF OIL INDUSTRY
2

GOAL #1:

• EVALUATE VERY-LOW SULFUR 

FUEL IN TECH-5 VEHICLES

• KEEP OTHER FUEL PARAMETERS 

CONSTANT

• USE 1, 30 AND 100 ppm S FUEL 

SULFUR LEVELS

• START WITH 1 ppm S FUEL, DOPE 

TO 30 AND 100 ppm S w MULTI-MIX
3

GOAL #2:

• EVALUATE FUEL OXYGENATE 

EFFECT ON EMISSIONS

• USE MTBE-CONTAINING CBF2 FUEL 

AND COMPARE TO ETHANOL FUEL 

AT 4% OXYGEN,

• AND TO OXYGENATE-FREE FUEL, 

ATTEMPTING TO HOLD KEY FUEL 

PARAMETERS CONSTANT
4

Emissions Class 1 TLEV 9 LEV 3 ULEV

Vehicle Class 9 LDV 2 LDT2 2 MDV2

Body Class 9 PC 4 T

SFTP Chip 3 Yes 10 No

Engine-Out Data 5 Yes 8 No

Catalyst Inefficiency 7 Yes 6 No

Bags 1, 2, 3 of FTP 9 Yes 4 No

Methane 11 Yes 2 No

"1" 13 Yes

Sulfur Fuels "30" 13 Yes

"100" 13 Yes

Emissions Class-Oxy 0 TLEV 8 LEV 2 ULEV

Vehicle Class-Oxy 8 LDV 1 LDT2 1 MDV2

Body Class-Oxy 8 PC 2 T

Ethanol Fuel "E" 10 Yes 3 No

Clear Fuel "C" 10 Yes 3 No

Reversibility Standard 12 Yes 1 No

Extra 8 Yes 5 No

US06 "U" 2 Yes 11 No

Other 2 w Species 4 w/o FE

Status of Industry CBF3 Low Sulfur Data Set:

Summary Information:
5

0.00

0.02

0.04

0.06

0.08

0.10

0 50 100

Fuel Sulfur Level, ppmS

E

mis

sio

n

s

R

a

t

e

,

g

/

mi

Fleet (13)

PC Fleet (9)

Trucks (4)

Tech 5 Model

NMHC
6

0.0

0.5

1.0

1.5

2.0

2.5

0 50 100

Fuel Sulfur Level, ppmS

E

mis

sio

n

s

R

a

t

e

,

g

/

mi

Fleet (13)

PC Fleet (9)

Trucks (4)

CO
7

0.00

0.04

0.08

0.12

0.16

0.20

0.24

0 50 100

Fuel Sulfur Level, ppmS

E

mis

sio

n

s

R

a

t

e

,

g

/

mi

Fleet (13)

PC Fleet (9)

Tech 5 Model

Trucks (4)

NOx
8

NOx-Wtd

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

0 1 2 3 4 5

ln(Fuel Sulfur)

ln

(

E

mis

sio

n

s

)

Linear

Tech 5

13-Vehicle Fleet Geometric 

MeansTLEV, LEV & ULEV PC & T

AAM/AIAM/Honda

Tech 5 Sulfur for CARB

 Emissions Reduction

30 ppmS

g/mi Species 30 to 1 Zero Lube

0.09 NOx 16% 55% 0.05 g/mi

0.90 CO 12% 69% 0.61 g/mi

0.06 HC 11% 58% 0.02 g/mi

Lube S???
9

CONCLUSIONS - SULFUR

• LINEAR ln(EMISSIONS) vs. SULFUR ppm

• FUEL SULFUR REDUCTIONS STILL 

NEEDED FOR HC, CO & NOx

• REDUCTIONS LESS THAN AUTO/OIL 

LOG-LOG PREDICTION AT 1 ppm S

• DIFFERENCE PRESUMABLY 

LUBRICANT-SULFUR CONTRIBUTION

• DATA SUPPORTS MAKING CARB TECH 

5-MODEL UPDATES

-- Effects observed are greater than ARB model 

prediction
10

OXYGENATE CONCERNS

• IMPOSSIBLE TO BLEND IDENTICAL 

FUELS AT 0, 2 & 4% OXYGEN LEVELS

• OIL INDUSTRY MADE GALLANT 

EFFORT, MUCH BETTER THAN COULD 

BE EXPECTED

• OXYGENATE EFFECT CAN RESULT IN 

CONFOUNDING ENGINE-OUT 

DIFFERENCES - LIMITED DATA
11

Fuel Analysis Data

Test Units <Non-Oxy> MTBE <EtOH>

10% F 145 141 136

50% F 210 202 205

90% F 297 294 291

Gravity API 61.4 61.9 60.2

Reid Vapor Pressure psi 7.1 6.91 7.1

Carbon wt. fraction 0.851 0.834 0.824

Hydrogen wt. fraction 0.141 0.139 0.142

Hydrogen/Carbon Ratio mole/mole 1.98 1.99 2.05

Sulfur ppm 35 31 28

Ethanol vol % 0.0 0.0 11.5

MTBE vol % 0.0 11.3 0.0

Composition, aromatics vol % 24.6 22.0 21.6

Composition, olefins vol % 4.6 3.4 4.1

Composition, saturates vol % 70.9 63.3 62.8

(R+M)/2 91.4 95.0 95.7

Net Heat of Combustion btu/lb 18347 18468 17776
12

Alliance Sulfur/Oxygenate Data

Error Bars represent one standard deviation 

0.00

0.05

0.10

0.15

0.20

0.25

0 20 40 60 80 100 120

Sulfur Content (ppm)

N

O

x

g

r

a

m

s

p

e

r

mile

NOx Data Set Clear Ethanol MTBE
13

Alliance Sulfur/Oxygenate Data

Error Bars represent one standard deviation

0.0

0.5

1.0

1.5

2.0

2.5

0 20 40 60 80 100 120

Sulfur (ppm)

C

O

g

r

a

m

s

p

e

r

mile

Sulfur Data Set Clear Ethanol MTBE
14

Alliance Sulfur/Oxygenate Data

Error Bars represent one standard deviation

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0 20 40 60 80 100 120

Sulfur (ppm)

N

M

H

C

g

r

a

m

s

p

e

r

mile

Sulfur Data Set Clear Ethanol MTBE corrected
15

Alliance NOx by Oxygen Content

Calculated Error Bars

y = -0.00221x + 0.13056

R2 = 0.35

0.00

0.04

0.08

0.12

0.16

0 1 2 3 4

Oxygen Weight Percent

N

O

x

g

r

a

m

s

/

mile

corrected
16

Alliance NMHC by Oxygen Content

Calculated Error Bars

y = -0.00201x + 0.05720

R2 = 0.82

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 1 2 3 4

Oxygen Weight Percent

N

M

H

C

g

r

a

m

s

/

mile

corrected
17

Alliance CO by Oxygen Content

Calculated Error Bars

y = -0.09131x + 1.22158

R2 = 0.93

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 1 2 3 4

Oxygen Weight Percent

C

O

g

r

a

m

s

/

mile

corrected
18

CONCLUSIONS - OXYGENATE

• SOME, BUT NOT ALL, OXYGENATE 

DIFFERENCES ARE STATISTICALLY 

SIGNIFICANT

• NOT CLEAR THAT MODEL CHANGES 

WARRANTED BASED ON THIS DATA