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.
Hi Powell,
You have some real misinformation here. VW has never warranted any biodiesel greater than 5% in their vehicles. You say ‘since about 2006′, but that indicates their position has changed, which it has not. In 2007 and 2008, there was no TDI, and in 2009, the new systems came out with DPFs. These are the systems that have oil contamination issues. But your article doesn’t have that level of detail.
The reason they allow up to 5% biodiesel is because the diesel specification was modified such that it can pass with that much biodiesel in it. In other words, “diesel” itself can be B5 and still be considered diesel.
Everything you have said here is just conjecture, and references conjecture by other people on forums – much of which is either based on conjecture on yet more forums, or is baseless.
I know you are a promoter of biodiesel, and aren’t trying to get people to NOT use the fuel; but you should also know that many people have used higher blends of biodiesel with no problems for many miles. It is generally agreed that one “should” change the engine oil more frequently than the recommended 10k miles – but that is a pretty easy trade off for most folks, who have been changing their oil at 3500 or 5000 miles for most of their lives anyway.
Thanks for doing what you’re doing, and please continue to look for facts on this issue. I just bought a 2011 BMW 335d specifically to test B100 and will be reporting the results on my blog (dieselgreenfuels.com/blog) when I get started.
Jason Burroughs
DieselGreen Fuels
Hi Jason,
Thanks for reading and taking the time for the comments. My understanding is that VW in Europe used to warrant ASTM6751 spec B20 biodiesel for at least the MkIV TDI. I don’t know if they still do. My assumption is that the fuel systems on the VWs in Europe are either the same or similar to the MkIV fuel systems in the US. My comments on the MkIV diesels are from my own testing of ASTM spec biodiesel in my two ’99.5 VW Jetta TDIs with only modified viton return lines. I have 270k miles on one and 320k miles on the other.
Thanks for clarifying about the comments on the newer diesels being conjecture. That’s actually why I specifically referenced the forums and linked to them. I hope that we find that the newer diesels wil run on B20 and greater blends of biodiesel!
Let me know how the 335d handles the biodiesel. Pioneers like you are the ones who will help us know the truth about what works and what doesn’t. I plan on buying the Chevy Cruze diesel when it comes out and will test it with B20 and B100.
-Powell