If you want to burn veggie oil in a diesel engine, it's best if you get an older vehicle with indirect injection, like an older Mercedes or Peugeot. Then if it screws up the injector nozzles, you won't have pure fuel squirting directly at the top of the piston -- which it can melt through like a blow torch.
The best advice for a TDI owner has already been given several times in this thread: DON'T DO IT! There is no way you can save enough in fuel costs to cover the potential repair costs.
The best advice for a TDI owner has already been given several times in this thread: DON'T DO IT! There is no way you can save enough in fuel costs to cover the potential repair costs.