"Before the switch to fuel injection and computerized controls,
engines were subject to damage from prolonged knocking. But today's
engine management systems incorporate electronic knock sensors, which
detect the condition and adjust the ignition to stop the problem. As
a result, it is almost impossible to hurt a current engine by using
87-octane fuel, industry experts say."


If you start retarding the ignition to adjust for pre-ignition,(that is how it "adjust") you will loose power and will have to make up for that power by more acceleration. More accelarator...less fuel mileage. So you save a few cents a gallon at the pump, but it takes more fuel to compensate.So how much are you really saving? Not worth it to me.