BMW Diesel Owners & Enthusiasts
MB emphatically limits the use of biodiesel to B5. This is from their literature:
http://www.mbusa.com/vcm/MB/DigitalAssets/pdfmb/serviceandparts/biodiesel_Brochure5.pdf
Count the number of times MB mentions that using anything greater B5 voids the warranty.
The photos were pretty convincing...