Re: '04 Jetta TDI

After much thinking about it and meaning to get around to it, I think I'm finally ready to delve into the biodiesel world. There's even a place in town that sells B20 and B99. My car is an '04 Jetta TDI with 22k miles on. I'm trying to figure out the right way to do this. As other people have mentioned, VW recommends a paltry B5 max, to which I have to ask, "what's the point?" Here in Tucson, it does get a bit chilly on winter nights, so the most I'm thinking of using this time of year is B20 anyway. Everything I've read everywhere seems to be quite clear that B20 can't possibly have any negative effects vs B5 or even full Petro-based diesel. The real question is about going to B100 once it warms up. I'd be curious to hear people's thoughts and experiences on this. Do I need to have any hoses or anything replaced? How about the fuel filter? Is my mileage low enough that I don't need to worry about it? Anyone had any nasty run-ins with VW WRT warranty problems from running higher than B5? Thanks in advance for any info!

I run a '03 pre-PD engine on B100 all summer, but do shift back to about 10% during the coldest months. If they had a pump with B20 I would run it without batting an eye, but B10 is all we have locally at a pump. (Cincinnati, OH) You've got a different story though ... as your PD engine has higher injection pressures and you need to avoid 'gelling' your biodiesel. (of course we all do, but your PD engine is less tolerant of bad fuel) I suspect that you are on the exact path that I would take: B20 in the winter and considering a much higher blend or straight "high quality" B100 in the summer. Go for it. As for warranty claims ... I suspect if you have injection problems brought on by bad fuel that you'll be looked at pretty close "if you tell them you're running B100." You better hope that your fuel supplier will stand by his product if the finger is pointed at the biodiesel.

Pardon the noob question here, but what's PD refer to in the context of a diesel engine?

Pumpe Duse, or "unit injector" technology. Instead of having a fuel injection pump, each injector has a pump built in that is actuated by extra lobes on the camshaft. VW has been using this technology for a few years instead of the common rail system used by Mercedes and most other diesel engine manufacturers. VW has abandoned PD technology, and will soon be coming out with CR systems. We have two non-PD TDIs and two PD-TDIs in the family. They all run on bio. Currently, we are running our winter blend of B80/K20, which is good down to about 10-15ºF with our homemade bio. You will not need to replace anything.