some use cooking oil without many problems. The new Pumpe Duse turbodiesels from VW may not like it (and apparently VW says using biodiesel will void the warranty).

[link|http://forums.vwvortex.com/zerothread?id=1272011|VWVortex] has some comments. It looks like [link|http://forums.biodieselnow.com/topic.asp?TOPIC_ID=1695|mice] might be a problem....

Cheers,
Scott.
(Who loves his Jetta PD-TDI but hasn't tried biodiesel.)