Fact: Although the higher octane in premium fuels may not effect the engine (yea, yea, except in knock) there are certain premium fuels that have excellent additive packeages that can really help an engine. Most of these additives are types of dergents that help clean carbon deposits off valves and combustion surfaces.
Fact: the octane number is reached by the (R+M)/2 method. You may have seen this on the gas pump, if not look sometime. The fuel is tested in a variable compression, single cylinder engine. It is tested in the research method (I believe at 1000 rpm) and and then in the motor method (I believe at 2000 rpm). These numbers are then added and diveded by two (averaged). The numbers come into play by increasing the compression until knock is acheived.
I forget how they derive the number from the compression setting, but the higher the number, the higher the resistance to detonation, not the resistance to combustion. We want the fuel to combust, but not controlled.
I am sure somebody will inform me of the actual rpm numbers, and i am sure somebody else is going to knock the detergent part, go ahead, you're retarded.