Paulgill, I have a friend that has been preparing biodiesel and has recently run one of the local city buses on a straight supply of it. He supplied me with 40 litres (10 US gallons) and I put it in my 300D which contained about 10 litres (2.6 gallons) of diesel. I made no changes in terms of fuel return lines or pump timing. It worked very well, most noticeable was how much more quiet the engine ran, especially at idle. I may have noticed a little harder starting but can't bee 100% sure as I've only put about 1500 miles on the car since I've got it. I would suggest introducing it as a mix to begin with and maybe have a extra set of fuel filters on hand. Good luck, Trent.

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67 250S
72 220D
80 300D
93 K1100RS
2000 Jetta TDI