Brumby from the data I have at work E-10 causes severe condensation in engines, fuel system components and tanks.. BMW offered no warranty support when E-10 first hit the bowsers, their policy has changed I believe, but to what I'm not up to speed with, at work we have been testing our engines with E-10 in the Dyno room with results that lets say are disappointing, we continue to monitor the status Quo, our warranty has not changed since it was introduced on the proviso that no more then 10% ethanol is used.... our engines have always used Stellite valves form inception and this helps, but other components are still being effected...