I'm wondering that too.it states you have to use 39% more fuel.I remember reading somewhere that it costs 2.65 a gallon for E85 and 91 octane around here is 3.15.that's a difference of 50 cents.if your gas tank is lets say 14 gallons and you get 23 mpg it would cost you $44.10 to fill with 91 octance gasoline and $37.10 to fill with E85 ethanol.You would be getting 322 miles per tank with 91 octane gasoline.You would get the same with E85 but it requires 39% more fuel to go the same distance so you'd need 1.39 gallons to go 23 miles.You basically would be getting 15mpg roughly if my calculations are correct.15 times 14 gallons is 210 miles.That's 110 miles less than regular 91 octane.But if you take the 7$ you saved by using E85 and put it back into the tank you'd be getting roughly 249 miles to the tank.

I'm done with my math for today.I need to link this to my algebra teacher

If the ppg would be at 2.35 it would cost $32.90 to fill up meaning with the money you save and put back in you'd get 281 miles a tank.So for it to be better for our wallets it would have to cost 2.05 a gallon.Meaning it would cost $28.70 to fill your tank.and you would save around $15.40 and putting that back in you'd be at 112+210 which is 322.

I think I might have did something wrong but you guys should get my point.you'd have to put the money you would save back into the gas tank.