Premium in some states is actually 89-91 octane. This is considered mid-grade in states with pollution regulations on the gas sold there. You could probabally get away with regular in CA, you will neeed to listen for pinging in your engine. To be safe run mid-grade most of the time with an ocassional tank of premium. The one thing your saleman didn;t tell you is that if you run a lesser grade of gasoline you will lose some mileage.