Good luck trying to prove your case in court.

My MB service adviser asked me to put my hand up, and swear on something that I hold dear to promise I would never put biodiesel in my CDI. He showed me a similar car in the service department that had the fuel system completely taken apart, with everybody pointing fingers for responsibility of a $3k bill that MB refused to cover under warranty.

As others have said, it isn't worth the risk, especially with the dubious environmental and economic benefits.