Modern cars have computers which can figure out what octane you are using. Up to a point, they will advance the timing more on higher octane gas, but only up to a point. You coult put 130 octane av-gas in it, and it would run crappy because the timing couldn't advance enough to start the gas burning.
Remember - higher octane means slower burning so the engine can fire the spark sooner (advance the firing) allowing a longer burn cycle which can (if the car is capable and most new cars are) yield higher power. Beyond the limits of the computer, higher octane is just a waste of money. I would believe 89 or even 92 would yield some better performance and mileage than 87, but somewhere between 89 and 92 the engine reaches its maximum advance capability and the rest, as they say, is wasted.
Remember - higher octane means slower burning so the engine can fire the spark sooner (advance the firing) allowing a longer burn cycle which can (if the car is capable and most new cars are) yield higher power. Beyond the limits of the computer, higher octane is just a waste of money. I would believe 89 or even 92 would yield some better performance and mileage than 87, but somewhere between 89 and 92 the engine reaches its maximum advance capability and the rest, as they say, is wasted.
