The Casey's convenience store/gas stations here in rural MO sell both "regular" 87 E10, and E15 which is .10 a gallon cheaper and 88 octane. shruggy
I agree that the mileage decrease will offset the slight cost savings (3.79 to 3.69 a gallon) and I'd also worry about effects on rubber/plastic parts of the fuel system in older cars.

Anyhow I run alcohol-free premium in the Dart's fuel cell smile