From what I'm reading, it is possible to put Biodiesel in the car. It's better for the environment, and it may even be better for the car. However, it may also eat through the hoses, and it may void the manufacturer's warranty.
There's a biodiesel station just northeast of Boston.
Looking a bit more, it seems like the "eating through hoses" has not happened in practice in recent model cars.
It seems also like the nearby biodiesel retailer only sells B20 mix biodiesel. Not as good as something like B100 would be, but a start at least, and I wouldn't want B100 until it's warmer anyway, since it gels at temps of around 30°F.
"One thing to remember if you're running biodiesel on an older car: the strong solvent properties of biodiesel will clean out the fuel system and can clog your fuel filter with old gunk. It's often a good idea to replace the fuel filter after your first few tanks of biodiesel." -- makes sense.
It does seems like VW of America can void a warranty based on using biodiesel. However, I'm not sure that the engine is still *under* a warranty, and even if it was, is there any way they could tell that you were running biodiesel (especially only B20, which is still 80% petroleum)? Just go through a tank, and load the next one up with good ole foreign oil diesel, and nobody the wiser?
Anyway, depending on cost (which I'll have to call and try and find out about) it seems like we may start filling up the Jetta with biodiesel in the near future. That'll be nice -- I'm all for things which are less shitty to the environment, I just never realized it was that easy until today for whatever reason.