Unless you advanced your timing, or your engine has high cylinder compression, or your engine is 'knocking' you don't need high octane fuel at all. There is absolutely no benefit in terms of power/reliability/fuel economy etc. The only difference is the higher resistance to detonation than 87-rated fuel. All the other additives (like detergents, anti-oxidants, rust-inhibitors, etc) are present in all fuel grades. Unless your manual says to use high octane fuel (because of the reasons mentioned above) you are just wasting money each time at the pump.