my gas vs your gas

[murcod]

Yes, I wouldn't say a higher octane spec than the minimum is wasted (and it certainly doesn't go out the exhaust pipe- that's for sure!)

[~tc~]

It's "simple combustion thermodynamics".

Octane is the resistance of the fuel to detonation. In other words, higher octane fuel has LESS energy than lower octane.

In a traditional combustion engine, however, compression ratio can more than overcome this. (I sum it up as "compression ratio cures all")

You want to use the LOWEST octane that will not experience ping/knock from predetonation for max power.

[davidbus159]

I recently read that Shell was the only "top tier" fuel available in my area, so that's all I use now (87 octane). Here's what influenced my decision: http://www.toptiergas.com/