Originally Posted by Alizarin

Funny enough, I was just reading some of the E85 FAQ today. Looks like you can use up to a 30% mix of Ethanol and gas (I guess 93 octane) with no problems on a stock ECU tune. People have been running 100% E85 with upgraded injectors for over 2 years on OEM fuel system parts with no detectable wear, corrosion, or problems other than one guy's fuel pump died because he was running 80psi fuel pressure.

In essence, they say to start with a low % mix, then slowly up the % until you are happy with the performance, or you throw the "System to lean" code, meaning that the ECU has run out of compensation room on the closed loop a/f. At that point, you back it off a little bit.