Published on June 3rd, 2009 | by Jennifer Lance

Biodiesel Blues: Car Manufacturers Say No to B100 in New Diesel Vehicles

A few years ago when we bought a new truck, we specifically purchased a diesel so we could use biodiesel in it. We had no intention of making our own fuel, but we were able to buy B99 at a local gas station. If you are new to biodiesel, the number refers to the percentage of biofuel in the mix. B100 is pure biodiesel. B20 is more common, as the percentage of biofuel is so low it does not congeal in cold weather.

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B100 no longer compatible with new cars and trucks

A recent announcement from VW, Mercedes, Nissan, Renault, Jeep, Ford Power Stroke, Ford E-series vans, Dodge Rams, Cummins 6.7 and Chevy Duramax states B100 is no longer compatible with their engines. I’m not sure if this news is prompted by the companies not wishing to honor manufacturer’s warranties on vehicles that run biodiesel or if they just realized the engines were not compatible. According to Popular Mechanics:

Until two years ago, all diesel engines were B100-compatible (biodiesel cannot run in gasoline engines because it needs an engine that ignites by compression). Then standards set by both the Environment Protection Agency and California Air Resources Board, phased in for 2007, required all passenger vehicles to meet the same, stricter emissions. That meant diesel manufacturers had to reduce emissions of NOX and particulate matter to meet those of gas-powered cars. These standards were created with good intentions—to look out for our health by improving the air that we breath. (After all, particulate matter is a known carcinogen.) But the way most manufacturers did this created a setback for those of us trying to use biofuels.

Of particular concern is the design of diesel particulate filters (DPF) that were created to reduce emissions on diesel vehicles. Popular Mechanics explains:

To get rid of particulate matter, the diesel manufacturers came up with what’s called a DPF (diesel particulate filter)…It captures particulate matter in its inner core. Periodically, the DPF has to be taken up to high temperatures to burn off the matter it has collected…Most of the manufactures decided to inject fuel into the cylinders just after the cylinder fires and the exhaust valve opens. At this point, the fuel vaporizes and the vapors move down the exhaust to the DPF and clean it. Because biodiesel is denser than conventional diesel fuel (it has a longer hydrocarbon chain) and has a higher distillation temperature and boiling point, it does not vaporize as easily. Some of the fuel ends up adhering to the cylinder wall and runs past the rings, diluting engine oil.

Our truck is older than two years, so hopefully we are still able to run higher percentages of biodiesel. For now, we will probably stick to B20, as I am not sure it is worth the risk and I doubt the car dealer would recommend we continue running B99. Actually, the point is rather moot, as Texaco bought our local gas station that provided us with biodiesel and stopped selling B99.