A4 biodiesel use
Roobob:
I was a big fan of biodiesel when I had my 2000 VW Golf TDI (A4). It would run fine on any of it whether it was B100, B50, B20 or B5. It has higher lubricity than the ULSD fuel currently available and may be beneficial to your engine which was build to use the old standard higher sulfur diesel. The problem with biodiesel is that you can't find winterized biodiesel for winter use; so it will gell below 30 degrees F.
If you can find it, use it if you like, but don't use it in winter in Chicago. I would suggest that you find a fuel station that has the highest quality USLD diesel in your area and then mix it with some B100 for the lubricity.
I'm not sure biodiesel will save the planet. I don't think the US has enough fallow farmland to replace the diesel needs of our country. And the price of corn tortillas has skyrocketed in Mexico, so they don't think it's a good idea either. LOL
Anyway, in an A4 TDI, it is clearly an alternative. Just know the limitations.
Norm!