Hi,
I have a V6 TDi 2001, and i have run it on 100% B100 Bio for over 12 months now, and its fine....
However a few fellow users of bio with newer cars "2004 +" seem to had little problems.
One guy has a 54 reg golf tdi and he has hot starting problems, so when the engine is warm it takes a few turns to start again, this seems to be related to the heater plugs not staying on very long when the car has been running.
Another guy has a 56 reg Passat Tdi, which has had a splutter or two when running on B100.
Both these people have found that running on a manual mix of 50% Bio 50% pump diesel or so resolves any running problems.
Thanks