The best info about fuel that I've found. It lays out the fact very simply. Its funny how much money people spend of fuel and they dont know anything about it.

http://www.chevron.com/products/ourfuels/fuel-school/browsetopics.aspx

"In most vehicles no benefit is gained from using gasoline that has a higher octane number than is needed to prevent knock. However, in some vehicles equipped with a knock sensor where the car's computer controls the engine to reduce or eliminate knock on lower octane grade fuels, a higher octane number gasoline may improve performance slightly if the cars's computer is controlling the engine to reduce or eliminate knock on lower octane grade fuels."

It used to be easy to refute (though never to stamp out) the "higher octane = more power" fallacy. Now things are more complicated, and the answer has to be "No, except..."