June 9, 2009

Biodiesel blend performs as well as ultra-low sulfur fuel

John Lumkes
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A new Purdue University study shows that there is almost no statistical performance difference in semitrailer trucks using B20, a 20-percent blend of biodiesel, and No. 2 ultra-low sulfur diesel, the current standard.

"In terms of performance, reliability and maintenance costs, it was basically a wash," said John Lumkes, the assistant professor of agricultural and biological engineering who led the study. "The only differences are environmental and economic."

The study, which compared two 10-vehicle truck fleets using the ultra-low sulfur fuel and B20, was released in the journal Applied Engineering in Agriculture. Trucks used for comparisons in the yearlong study had the same engines, similar miles already on them at the start and drove nearly the same number of miles over the year.

The only statistical difference related to the B20 was that it lowered the oil viscosity between maintenance intervals in engines slightly more than the ultra-low sulfur diesel. But even so, Lumkes said the oil still had sufficient viscosity so as not to damage engine parts.

"They were still within the range of what is acceptable before you need an oil change," he said.

The study followed each fleet's idle time percentage, average speed, engine load percentage and engine speed. Each pair of trucks had close to the same statistics in each category.

At the end of the study, each fleet of 10 trucks had driven more than 1.5 million miles. Differences in performance based on fuel economy, fuel test results, engine oil analysis, and service and maintenance costs were considered minute. B20 cost about 13 cents more per gallon during that time than the ultra-low sulfur diesel.

Lumkes said his study could ease concern about the effect biodiesel has on engine durability. He said some engine manufacturers are wary about extending warranties to those who use biodiesel because not enough has been known about how the biodiesel affects engine wear.

"This shows that there is no observable difference in performance of engines using biodiesel versus the more common commercial fuel," Lumkes said.

Lumkes added that the quality of the B20 also is an important factor. All the fuel sampled during the study exceeded the National Biodiesel Accreditation Commission standards.

The Indiana Soybean Alliance provided funding for the research, and a private company that provided the trucks also provided funding.

Writer: Brian Wallheimer, (765) 496-2050, bwallhei@purdue.edu

Source: John Lumkes, (765) 494-1173, lumkes@purdue.edu

Ag Communications: (765) 494-8415;
Steve Leer, sleer@purdue.edu
Agriculture News Page

PHOTO CAPTION:
John Lumkes found that a 20 percent blend of biodiesel fuel performed as well in trucks as the standard ultra-low sulfur diesel. Differences in the fuels' performances were statistically insignificant. (Purdue Agricultural Communications photo/Tom Campbell)

A publication-quality photo is available at https://www.purdue.edu/uns/images/+2009/lumkes-biodiesel.jpg

A study was performed on 20 Class-8 trucks paired by make, model, mileage, and drive cycles. Ten trucks were operated using #2 Ultra-Low Sulfur Diesel and 10 using a 20% soy methyl ester blend (B20). All trucks were equipped with data collection units that monitored engine information including fuel consumption, idle time, truck speed, engine load, and engine speed. Data collection occurred over a continuous span of 12 months. In addition to operating data, laboratory-based fuel and engine oil testing was performed to quantify the analytical differences between the two fuel types. Cetane number, energy content, density, kinematic viscosity, and lubricity was measured for both fuels and at every oil service interval engine oil samples were evaluated based on fuel dilution, soot content, wear metals, contaminant metals, viscosity, oxidation, and acid/base number. Operational and maintenance issues such as cold start reliability, fuel filter service intervals, and general engine maintenance was also analyzed for each fleet. Statistical analysis was performed to determine significant differences in the performance of engines on these #2ULSD and B20 fuels. At the conclusion of the study minimal differences were found with most comparisons, the exceptions primarily found in differences between the engine oil samples based on the two fuel types used in the study. These differences included viscosity, acid/base number, oxidation, and lead wear which indicated slightly higher oil degradation levels with B20 use.

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