Ok, Octane........ (I have said this before) The lower the BTU of a fuel the higher the octane, the higher the BTU of a fuel the lower the octane and it is the higher BTU that makes the fuel more likely to cause detonation, and the lack of octane that can cause a engine to knock (Known as pre-ignition or autoignition). Therefore Higher Octane fuels won't always make more power and can make a vehicle with low compression pistons run worse and be harder to start due to the lower BTU of the fuel. Most modern engines do let you have a noticeable difference in the fuel you run as its management system will adjust to the octane/BTU of the fuel you are running. Race engines obviously need the high octane to stop them from coming apart,(high compression/RPM) not to just make them run better.
Now as for E85..... It is a complete pile of shiit and
"LIES" that it is cleaner for the enviroment. Yea it will have lower NOx and CO, but that is because of the lower BTU of it (time and temperature above 1200F makes NOx, now your running cooler so therfore less NOx). But it is that Lower BTU that opens up another whole can of worms. By burning lower BTU you create lower combustion temperatures. Well guess what, burning at a lower temperature creates more formaldehydes, acetaldehyde, ozone and unburned hydrocarbons commming out the tailpipe, and that is the stuff that is making kids sick, causes asthma and numerous breathing problems. E85 increased ozone-related mortalities in the United States by about 200 deaths per year compared to gasoline. I work as an Emissions tech, I have 22 years in this trade, I have grown up in it, take my word for it, it is a complete coverup. I have an FTIR analyzer (uses light and mirrors

I swear it's magic!) that can see this and it is really really bad what comes out the tailpipe of a car running E85. The Greenies and the idiot comercials are full of shiit about it. It's not a green fuel!!!!! It takes hundreds of gallons of water to produce one gallon of ethanol for Christ sake! Corn ethanol, produced in any quantity to make a difference in oil imports, will take massive amounts of land, destroy habitat and forests, and threatens the world food supply. Corn is food! NOT FUEL!
Mark my word and it is comming down, that soon we will not be regulated by CO and NOx, but by the CO2, formaldehydes and hydrocarbons comming out the tail pipe. It is just arround the corner as it is not about emissions, but about dollars.
Geeeesssssh! This E85 being cleaner bullshiit just makes me fuucking mad!
Ok end rant.