i'd say no.
i can get gas with no ethanol added, it runs about $3.35 a gallon down my way. it's better than the 10% corn crap.
every car is different, though. the only way to know for your car, is run a full tank of 87, reset your trip meter, drive around, run it out, fill it up and with those gallons, you can calculate MPG (mileage driven divided by gallons at fill up). then repeat that, using E85. try to do the same driving, as in don't run highway on the e85 and compare it to stop-and-go city traffic when you're running the 87.
i calculate mileage if i modify air intake, or add an exhaust system, tune the ECU, things like that.
actually, check your car. you might be stuck running premium, or 93...that would suck.