Biodiesel’s New Approval Rating Could Ease Warranty Concerns

Dodge Biodiesel Ram Truck

Lack of warranty support for biodiesel has been a major stumbling block for new diesel owners who want to start using the fuel. But three long-awaited ASTM specifications could help change that.

Automakers and engine manufacturers have been requesting a finished blend specification for B20 biodiesel blends for several years, with some citing the need for that spec as the single greatest hurdle preventing their full-scale acceptance of B20 use in their diesel vehicles.

On June 19th, after more than five years of research and discussion, the American Society for Testing and Materials (ASTM) finally approved the following specifications for biodiesel fuel:

  • Changes to the existing B100 biodiesel blend stock specification (ASTM D6751)
  • Finished specifications to include up to 5% biodiesel (B5) in the conventional petrodiesel specification (ASTM D975)
  • A new specification for blends of between 6 percent biodiesel (B6) to 20 percent biodiesel (B20) for on and off road diesel.

If that’s gibberish to you, here’s the take home message: the new specification for B6-B20 biodiesel blends could prompt more automakers to fully support B20 in their new cars and trucks.

Anyone who’s ever seriously looked into buying biodiesel for a new car or truck knows that manufacturer warranty approval of biodiesel is all over the map.

For example, Chrysler supports a B20 biodiesel blend in 2007 Dodge Ram trucks like the one above—but only for use in government or commercial fleets. GM also only supports fleet use of B20, but supports B5 in all commercial vehicles as do Ford, Mercedes, and VW. (Interestingly enough Case IH and New Holland, two manufacturers of $200K+ agricultural machines both support B100.)

Automakers: Could You Please Start Supporting B20? Thank You!

Why don’t automakers provide better support for biodiesel? The most (seemingly) reasonable explanation I’ve been given has to do with biodiesel’s ability to withstand the incredibly high pressures and precise specifications of the new common rail fuel injection systems, which also could apparently impact the ability of new clean diesels to meet NOx emissions standards.

But I’m going to need to see some numbers before I buy that, since biodiesel is already cleaner burning than diesel fuel anyway. I’m also not convinced that biodiesel wouldn’t work in high-pressure situations when diesel does.

I fired a few questions at VW about this, after test-driving the new clean diesels earlier this month. All I got was:

“There are studies taking place that suggest we won’t authorize anything beyond B7.”


“Anything higher than a B7 mixture may degrade the burn thus the potential for negatively impacting emissions”

The keyword there is may. I’ve never seen any evidence that biodiesel would not work at a B20 blend in these newer engines, and hopefully these new standards will further ease any concerns automakers might have.

Final Words:

The new ASTM spec for B6 – B20 is a major building block in GM’s efforts to elevate biodiesel as part of our overall energy diversity strategy.

-John Gaydash, Director of Marketing for General Motors Fleet and Commercial Operations

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Photo Credit: skidrd via Flickr under Creative Commons License


In a past life, Clayton was a professional blogger and editor of Gas 2.0, Important Media’s blog covering the future of sustainable transportation. He was also the Managing Editor for GO Media, the predecessor to Important Media.