This is a question answered from a VW website that is for VW employees. I hope this helps some. We had another customer last week state the same to us and the guys in service will tell you, they drive TDI's and use the diesel that is in IL. One service guy told me he prefers Casey's diesel to others. Here at Auffenberg we fill out TDI's up at Circle K.
For our TDI engines: Volkswagen currently recommends that you use standard diesel fuel, or biodiesel blend fuels of up to five percent (B5), purchased from a mainstream retailer through a commercial pump.
“Biodiesel” does not include homemade “bio-fuels” or home brewing, because the production process cannot be controlled in an adequate manner. Fuels which do not meet the ASTM specifications are NOT approved.
Volkswagen is fully aware of the “BioDiesel” matter you speak (states moving towards B20)
Volkswagen and Archer Daniels Midland continue to conduct research regarding the use of biodiesel blend fuels, including higher level blends such as “B20” (20 percent biodiesel, 80 percent petrodiesel), as well as to develop appropriate specifications that will assure the suitability of such fuels for use in our vehicles.
I anticipate dealers will soon see a “letter” of some sort stating the VW position on the use of B20 in those affected states (MN, IL, PA, etc.) I have no idea exactly when to expect the letter, but rest assured that it will be concerning the use of BioDiesel with levels higher than B5.
You understand that I cannot “officially” comment on warranty issues until then….but in my opinion, your TDI customers should not worry.
Until then…please stay tuned and be patient…..there is light (and BioDiesel) at the end of the tunnel!