e85 is like 6:1 air fuel for a good mix... terrible terrible fuel mix will result in even worse gas mileage. Run meth and 94 octane aand you can reach for the stars... i wont even consider e85 although its near me
By not considering E85 you are doing yourself a disservice. Ive got multiple local cars getting 20+ MPG on E85 open loop tuned 3800s. Also, the max power AFR of E85 is more broad then pump gas... not to mention its more forgiving if you were to have fueling issues that make you go lean (you probably wouldnt blow up).

E85 in standard engines - Wikipedia, the free encyclopedia