You might see a slight bump in fuel mileage using non-ethanol fuel but it's probably not going to be enough to offset the added price. Run a couple tanks then calculate the cost/savings.
I don't know about adding ethanol to gas specifically to raise the octane rating some fuels. A few years back ethanol replaced MTBE in gas as an oxidizer in the fuel. You've probably heard of oxygenated fuel? That's what it's there for.
At least in Washington, E10 is pretty much the standard fuel now. Although there are a few places that carry non-ethanol gasoline I never bother to go out of my way for them.
Last edited by Blazin72; 04-02-2014 at 10:50 AM.