[denverpete]

Increasing your octane level beyond what is recommended by your car manufacturer is a complete waste of money and will not result in any power gains. There are some good threads about gas around here.

It's an unfortunate belief that the higher the octane the more power the gas has. It's actually the reverse since most, if not all, octane boosters contain additives which have less caloric value than petroleum. This leads people to spend more money in the mistaken belief that they are giving their car a "treat". The only thing octane does is prevent premature detonation (or knocking). The higher the engine compression, essentially the higher the necessary octane rating.

So, unless you've done some work on your car to get a really high compression ratio - you don't need any higher octane than that recommended by the manufacturer. If you're already putting in the right octane - adding anything is just a waste of money...