I own two Volkswagen Jetta TDI Mk IV diesels from 1999 that run great on all types of biodiesel. The TDI engine from that period was the last of the great multi-fuel diesel engines with little modification. All of the fuel hoses are biodiesel resistant except for the fuel return lines which take about 10 minutes to replace with a viton hose kit from Greaseworks in Oregon. I made this slight modification to both of my Jettas and have been running all blends of biodiesel in them for years.
Since I advertise my use of biodiesel with bumper stickers, I’m often asked about what new vehicles are good for running biodiesel. For this reason, I’ve done some research on new diesel cars and trucks and what I’ve found is disturbing for the biofuel movement. Since about 2006, the Volkswagen diesels will only warrant biodiesel at a blend of B5. I would hardly even call that biodiesel since it is really only using it as an additive.
From what I’ve read on forums of real biodiesel users, this limit is for good reason. The electronics that control fuel flow and injection on the newer diesel engines don’t appear to be designed to run anything except for petroleum-based diesel. According to some experts, the minor differences in viscosity and cetane rating cause problems for the newer engines and can lead to mechanical issues.
The new BMW 335d diesel here in the US also only warrants up to B5 in their diesel engine. Experts on the BMW forums indicate that the BMW diesel uses a high pressure injection system similar to the VW TDI and will have trouble injecting biodiesel blends greater than B5. Higher blends contaminate the oil requiring much more frequent oil changes. They can also cause problems for the emission systems.
As US manufacturers begin offering domestic diesel cars, we need to make sure they use fuel systems compatible with at least B20 blends of biodiesel. If this issue concerns you as well, reach out to the manufacturers and ask them to engineer support of bioidesel into their engines. GM just announced yesterday they will bring the Chevy Cruze diesel to the US so let’s start with them and tell them we want biodiesel-compatible diesels here!
For now, it looks like I’ll need to continue maintaining my older VW diesels to preserve them for the future.
