Please note Don is talking about 2 very different numbers here, 87, 85 is octane rating, While E85, the 85 represents the percentage of Ethanol in the fuel, 85% ethanol, 15% gasoline.
I would not recommend E85, the rubber in our carbs was not designed for it. E10 is very common (hard to buy fuel without ethanol now 'round here) and will be fine.
As for performance, you won't get a bump from running 92 or higher octane. higher octane has a higher resistance to pre-detonation, the fuel itself doesn't contain more energy than the lower octane fuels.
Vehicles of course designed to run on it will have an advantage, as they require higher octane due to higher compression, the hi compression giving the performance gain, not the fuel.
Modern vehicles with knock sensors designed for 92 or higher fuel will run normally on 87, but performance will be reduced due to the computer adjusting the timing. One of my cages has a big 24v V6 in it, 250 hp. Running 87 just fine, but I can feel a performance difference, and the mileage is worse. More expensive mid-grade fuel pays for itself with every tank with improved mileage.
