1. Purdue University B20 Fleet Demo Project
Executive Summary
Purdue University researchers recently completed a major 12 month over-the-road/long haul
fleet study in the northern US that examined fuel economy and engine oil analysis encompassing
a fleet of 20 heavy-duty (Class 8) trucks, 10 which ran on soybean-based B20 and 10 on #2 Ultra
Low Sulfur Diesel (ULSD). The diesel fuel portion of the B20 was ULSD. Total distance run
by all vehicles exceeded 3 million mile, almost exclusively on a ‘freeway’ driving cycle and fuel
economy for the B20 and ULSD fleets were 6.97 and 6.91 miles per gallon respectively which is
statistically insignificant. Trucks operating on the B20 blend level had similar engine oil
analysis results and in both fleets filter plugging was an issue, which was determined to be
caused by the ULSD. However, no issues were seen in the winter months with starting nor were
any differences in maintenance schedules between the two fleets observed.
Fleet Study
Researchers Cody McKinley and John Lumkes with Purdue’s University Agricultural and
Biological Engineering Department in Lafayette Indiana examined fuel economy and engine oil
analysis in a fleet of 20 heavy-duty (Class 8) diesels one-half running on a blend of B20 and the
other on #2 Ultra Low Sulfur Diesel fuel. Within the 20 trucks, two were International and all
others Volvo with the model years ranging from 2003 to 2007. The study took place over the
entire 2007 calendar year with routes run in Indiana and the
surrounding states. The main objective of the study was to
determine the effect of a B20 blend on engine performance
(fuel economy and lubrication oil). All 20 vehicles employed
an electronic injection system which was monitored
throughout the study with extensive data collection of engine
load, vehicle and engine speeds, and idle time.
Biodiesel
The biodiesel was obtained from Renewable Energy Group and Peter Cremer, national
producers, both BQ-9000 certified. Biodiesel in the form of B100 was shipped to a regional fuel
distributor, CountryMark where it was rack injection blended. Over the course of the year long
study, the average price for B20 was approximately $2.93 per gallon while the #2 ULSD was
about $0.13 less. Cetane numbers for the B20 and ULSD were 56.4 and 55.6 respectively, while
the CFPP for the B20 blend was seven degrees less than the ULSD. The B20 energy content was
about 1% less than the ULSD.
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2. Truck Fleet
The fleet of trucks consisted of 2 International 9200I vehicles and 18 Volvo VNM 64T’s and
throughout the study like vehicles were paired with each other with respect to routes traveled,
odometer readings, and tires and transmissions. Table 1 presents data for the B20 and ULSD-
fueled fleets concerning the similarities encountered at the completion of the testing.
Table 1 – Pertinent Fleet Data.
Parameter #2ULSD Fleet B20 Fleet
Distance Travelled, mi 1,524,601 1,517,758
Idle Time*, % 17.6 17.7
Vehicle Speed*, mi/hr 45.1 44.7
Engine Load*, % 38.5 38
Engine Speed*, rpm 1290 1283
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Fuel Economy Analysis
Each truck was monitored for fuel economy through an on-board electronic monitoring system
for accurate fuel consumption data. The paired trucks had fuel economies of 6.86, 6.48, 6.88,
7.23, and 7.14 miles per gallon for the truck model years of 2003 through 2007 respectively.
Figure 1 shows the monthly fuel economy for each fleet. Statistical analysis of all fuel economy
data indicated that fuel economy differences across both fleets was insignificant. The
researchers also found that as the ambient air temperature increased, fuel economy also increased
for both fleets and the opposite was true in colder months. This fluctuation in fuel economy was
caused by a change in aerodynamic drag forces due to changing ambient air density.
Figure 1 – Monthly Fuel Economy Comparison (B20 and ULSD).
B20 Fleet #2ULSD Fleet
3.5 8.2
3.0 7.1
2.5 5.9
2.0 4.7
1.5 3.5
1.0 2.4
0.5 1.2
0.0 0.0
Month
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3. Engine Oil Analysis
Chevron Delo 400 Multigrade 15W-40 was used for all 20 vehicle and was changed on 30,000
mile intervals across the fleet. Analysis of engine oil samples indicated no appreciable changes
in both fuel dilution and soot content between the two fleets. Also, fuel type did not affect the
following metals: copper, aluminum, chromium, silicon, sodium, and potassium. However,
changes did exist between the two fuels with respect to viscosity and oxidation. Both fuels
experienced a statistically significant decrease in viscosity throughout the 12 month test, but the
lower viscosity levels were still within the acceptable range for engine oil viscosity. Oxidation
values for the B20 were higher than the #2 ULSD, but still much less than those that would
indicate abnormal oxidation.
Fleet Study Conclusions
Twenty Class-8 trucks, ten (10) operating on #2 Ultra-Low Sulfur Diesel and ten on a 20% soy
methyl ester blend (B20), were tested in the Midwest over a period of 12 calendar months with
each fleet accumulating over 1.5 million miles. Overall differences between the two fleets with
regards to fuel economy, fuel test results, engine oil analysis, service and maintenance, and fuel
prices between the #2 ULSD and B20 fueled trucks were found to be relatively minute.
No differences between the two fuel types were found with the following tests: fuel dilution, soot
content and nitration. Also, fuel type did not affect the following wear metals: copper, aluminum
and chromium nor silicon, sodium, and potassium. Viscosity of the two fuels did decrease with
the B20 showing a greater reduction, but both still within acceptable limits. Lubricity of the B20
was significantly greater than the #2 ULSD by nearly 50% in wear scar diameter tests.
In general, the B20 fueled fleet performed very similar to the #2 ULSD fleet in terms of fuel
economy, fuel properties, engine oil samples, and operation and maintenance issues with each
fuel having minor advantages and disadvantages in certain aspects of operation. Overall, B20
was demonstrated to be a feasible alternative to petroleum based diesel fuel for on-highway
trucking fleets.
For more information, contact John Lumkes at Purdue University (lumkes@purdue.edu).
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