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Most manufacturers approve the use of at least B5, with no impact on the warranty as long as the fuel complies with the ASTM D 6751 specification for biodiesel. On certain engine models, blends up to B30 have been approved.

The hurdle to widespread manufacturer approval of higher blends appears to be adequate testing time for the new electronic engines.

"We are in the process of validating the biodiesel percentage that will be allowed for use in our technologically advanced 2007 on-highway diesel engines," says Stearns.

"We really want to get some testing time with the electronic engines to make sure we didn't miss anything in the analysis," agrees Richard Hall, product planning and process improvement, Case Construction Equipment. "The mechanical portions of the fuel delivery systems are very common between mechanical and electronic engines. But the electronic engines have a lot more sensors that adjust fuel based on certain engine operating parameters. That's what we are trying to monitor."

Power output
B100 biodiesel contains less energy content than petroleum-based diesel. "Round figures, you get about 140,000 BTU out of a gallon of petroleum diesel and you get about 130,000 BTU out of a gallon of 'neat' biodiesel," says Borgman.