octane

[Power Hungry]

Like 408 said, unless you're running high compression or forced induction, there's not much benefit to running anything over about 95 octane. Higher octane doesn't make more power on a low compression engine, it just resists detonation/preignition.

Another thing to keep in mind is that high octane fuels such as aviation fuels are "drier" than normal automotive grade fuels. This can possibly result in advanced wear of the exhaust valves. This used to be a much bigger problem years ago with cars designed to run leaded fuels, but even today's vehicles which run hardened exhaust seats and alloy valves can still see accelerated wear due to the lack of lubricant additives in aviation fuels. Even many motorcycle manufacturers do not recommend running these types of fuels in 2-stroke engines due to the lack of lubrication on the rod bearings, rings, and piston/cylinder surfaces.

This is a very interesting article on fuel octane and is worth the read if you have about 30-40 minutes to kill. (I read kinda slow, too.) http://www.turborx7.com/fuel.htm It even has a section on octane, performance, and tuning. I hope it's useful.

Take care.