10% ethanol, wheres the break even point?

[2000mc]

so i was filling up with 89 octane 10% ethanol today (my usual fuel choice) for $3.45/g when i remembered thinking that at some point, paying and extra$0.10/g for straight gasoline is a better value. (in iowa 10% ethanol has been $.10/gal cheaper than straight gas for years)

but at what price are the fuels of equal value? i've heard E10 has 3-6% less btu's. even going with 3%, i'd be losing money paying more than $3/gal, i'm thinking. i've also heard that btu's don't necessarily indicate mpg, and that some ethanol can actually improve mileage. does mileage improve 3-6% using straight gasoline over 10% ethanol?


anyone else have helpful info on this, am i just a fool for running 10% ethanol?