In theory, all engines are capable of admitting a small percentage of biofuel mixed with regular fuel without further changes. Actually, a lot of U.S. states and countries around the world already have a small percentage of ethanol added to gasoline (or biodiesel into diesel).
Nevertheless, a few days ago, BMW published a press release and said that all BMW diesels are capable of being run with blends of up to seven percent of biodiesel (B7) without further changes. Regarding ethanol, BMW said that all BMWs are able to run with up to 10 percent blends, if the engine was built after 1998. For older engines, blends up to 5 percent can be also used.
The announcement was made because German gas stations will have a new type of fuel called "Premium plus" which includes a 5 percent blend of ethanol (E5), as well as B7 pumps available almost at every location around the country.
And what's more interesting, BMW also said that the company is waiting until second-generation biofuels arrive before developing E85 versions of its engines. The Bavarian marque also said that none of its engines are E85 or B100 compatible right now.