On a Feb. 5 panel in San Antonio, Caterpillar and Detroit Diesel representatives reminded National Biodiesel Conference attendees that their companies support biodiesel – but only certain types and blends in certain pre-2007 engines.

Moreover, their warranties won’t pay for damage caused by any bad fuel, including biodiesel.

For example, Hind Abi-Akar of Caterpillar said: “Use of acceptable biodiesel blends does not affect Caterpillar warranty. But if bad fuel clogs a filter prematurely, that is not a defect in materials or workmanship.” Therefore, she said, it isn’t covered.

By “acceptable,” Caterpillar means biodiesel that meets D6751 or EN 14214 specifications in blends up to B30, or 30 percent biodiesel to 70 percent traditional diesel. Detroit Diesel, on the other hand, specifies D6751 biodiesel and approves only B5 blends.

Moreover, said panelist Mesfin Belay of Detroit Diesel, his company approves biodiesel made only from rapeseed or soybeans, not from other feedstocks such as sunflower seeds and palm oil.

The sometimes complex biodiesel specifications of these and the other Class 8 engine manufacturers are available from dealers and on company websites. The panelists’ point was that biodiesel use, however promising, is not without tradeoffs.

Caterpillar strongly supports sustainable fuels and the reduction of greenhouse gases, but running biodiesel fuel still involves risks, Abi-Akar said. “There is a clear need for robust technical standards and higher quality and consistency in biodiesel fuels.”

Belay agreed. “DDC supports biodiesel,” he said. “It means reduced oil dependence and helps the environment.” However, he added, Detroit Diesel “will decline to cover a repair under warranty if biodiesel is causing the problem. The main issue is inconsistent quality.” For that reason, Detroit Diesel supports the voluntary BQ9000 quality standard created by the National Biodiesel Board, Belay said.

For the 2007 engines – which incorporate diesel particulate filters and run on ultra-low-sulfur diesel fuel and new engine oil — the jury’s still out, both Abi-Akar and Belay said.

“On-highway requirements are under review,” Abi-Akar said. “Engine testing is under way with biodiesel blends in order to determine biodiesel requirements.”

Detroit Diesel is testing biodiesel in 2007 engines in concentrations as high as B20, Belay said.

The manufacturers offered other cautions to Class 8 biodiesel users. For example, biodiesel acts as a solvent and may require extra filter changes because it clears dirt and sludge from fuel tanks, Belay said.

Oil analysis, a good PM strategy for all diesel users, is “strongly recommended” for biodiesel users, especially for blends B5 and up, Abi-Akar said.

Another speaker, Don Reese of Case IH, pointed out one reason for that: Biodiesel tends to accumulate in the crankcase, which thins out the oil. “Low evaporation rates means it remains in the oil longer,” he said.

Other panelists included representatives of DaimlerChrysler, General Motors, John Deere and Volkswagen.