You cannot run higher than a 20% blend without problems to the vehicle. Hence E-85 (85% ethanol)... Bad. E-85 is around 115-120 octane; however ethanol is also a very good solvent and will eat rubber hoses and o-rings at such a high concentration. Also Ethanol contains less energy than gasoline so it takes more to burn. Which is why you need a flex-fuel, safe fuel system and a computer that will recognize the Ethanol and change parameters.