NE Chicago Suburbs near the Highland Park / Deerfield area checking in with you. Myself, I personally enjoy the 2005 Passat TDI Wagons.
-- There are several websites that are endorsed by the Illinois soybean growers and Illinois farm bureau. Try this link --http://biodiesel.org/ .
In the search box just type in retail locations or retail pumps and you will find every retailer and supplier. You can always call them.
In order to qualify for Illinois state fuel tax incentives you have to use B12% or higher concentrations. I for one always use B20% ULSD Bio-Diesel and this is what I use in the Passats and my 2016 Duramax 2500HD truck. I have used the B20 for years and I have never had any concerns or issues. We do treat the fuel with Power-Service ( white bottle) and I change my fuel filter every year in about November as a maintenance measure. General Motors also allows up to B20% in the Duramax without messing up the warranty. I believe VW also allows up to B20 use. The fuel smells cleaner, burns cleaner and the car runs better on B20. Suffice to say; I would also bet a small wager the entire VW Dieselgate scandal would be a non issue and a non EPA concern if Volkswagen and the EPA had tested the affected cars (2009-2015 TDI engines) with a high quality B20 fuel.
I really think it is a superior fuel and you can tell a huge difference when you use it.