While E85 is an excellent fuel source for some vehicles, complications such as clogged injectors, damage to non alcohol-resistant engine parts and piston damage can occur. However, the engine damage potential from E85 is much lower than that of other available ethanol-based fuel solutions, such as E10 or E15.
Ethanol-based fuel should only be used in vehicles designed for "flex-fuel" usage; however, E85 is the safest of the available flex-fuel alternatives. Ethanol-based fuels can clean rust, sludge and other undesirable elements off of engine parts, leading to possible clogging of fuel pumps and injectors as these elements make their way through the engine.
Additionally, ethanol-based fuel has been observed to cause corrosion to aluminum vehicle parts. The higher ignition point of ethanol can also cause piston damage due to the higher engine temperature. Vehicles not designed for E85 usage also have incorrect oxygen-to-fuel ratios when using ethanol-based fuel.