[RoundelM3]

According to the owner's manual, E85 is specifically not recommended for the engines in current BMWs - the fuel systems are not equipped for it, and damage could occur with long-term use. If you run E85 and develop fuel system problems or other types of issues or damage to the engine, your warranty won't be honored. That said, almost all gasoline these days contains a certain percentage of ethanol, but not 85% like E85 - more like "may contain up to 10% ethanol", as it says on the pumps. So if you stick with no more than 10 to 15 percent, it will probably be diluted enough not to cause damage. The other factor is that ethanol is "hygroscopic" and will retain water/moisture unlike gasoline, so there is a possibility of injector damage. It's like it says on over-the-counter drugs - "please read the label carefully and use only as directed".