[Hotfingrs]

First the easy part....AV gas burns slower, because of the conditions air plane engines are subject too, and oxygen at different altitudes. Don't know all the specifics, but something along these lines.

Octane, is the gases ability to control detonation. The higher the number the more control it has. A 9.5-1 needs more than a 13.0-1. You might want to advance the timing on your 9.5 and more octane will help control detonation. More timing=more power. If you use more octane than you really need, you're just wasting your money.

There's a lot more that goes into this.....but this is the short version....as I know it.