No problem Justin, I ran race fuel in mine with no problems, as long as you flush it out before storage.
Oxygenated fuel can turn valves and seats rusty if not flushed out.
Sam.
Good to know, Sam. I thought ethanol-free race gas was okay to keep in the tank, especially compared to ethanol-based fuels getting gummy with non-use.
The really nasty part of the ethanol gas is: it absorbs moisture from the air, then mixes it with the gas as a heavier-than-gas molecule. After a winter of this, you will find a layer (about 10% deep, if your mix is 10% ethanol like ours) of brownish-colored gas in the bottom of the tank. This is the (ethanol + water) stuff, and it causes rust, even where the tank is wet (like, a form of underwater rust) because it is oxygenated, as well.
I have found that mixing in either Marvel Mystery Oil or even regular 10w Valvoline with the last tank of the season inhibits the water. I am currently experimenting with this again now, as the riding season here is pretty much over.
The octane question: higher octane burns slower than lower octane. Ethanol burns slower than both. The higher-compression engines need the higher octane to resist self-ignition in that hotter head: ethanol does this all by itself, being just plain difficult to ignite. Usually, if you burn higher octane than you need, it will tend to foul the sparkplugs if it does not make any performance difference (i.e., the engine does not need it, so some of it does not burn).
For example: my 750 will run fine in city traffic on 87 (midgrade) fuels, but is not happy at the 80-90+ freeway speeds we have here. The premium gas wakes up around 5000 RPM on my bike, so as I approach the 80 MPH mark with premium the bike just takes off into it (as this is where the cam starts it work). If I have the midgrade aboard, I have to roll on more throttle to pick it up. But...if I run premium all the time in mostly city surface street traffic, it will starts fouling the plugs after about 1500-2000 miles.