There's absolutley no point getting a higher grade of gas than recommended with a standard compression engine - anything more is a waste of money. Octane is just a rating of how well the fuel withstands compression before it auto-ignites (which is what "pinging" is), so having fuel that can withstand more compression than your engine can deliver is useless.
Fuel companies would have you believe that some of the additives in the "premium" fuel make it worthwhile because they "clean" your engine... however in an engine fitted with carburettors at best the additives do nothing, and at worst they clog up the jets.
Matt
