Tell you what, my brother flies airplanes (Cesnas and little guys like that there)...I took him to Palwaukee Airport in Illinois to fly back to Minneapolis and he fueled the plane up with 103 octane aviation fuel and I snuck a half of tank of this non-taxed fuel into my BMW. All it did was make the engine run hotter, no performance increase at all, in a non-catalytic 1976 BMW 2002. That was my first clue as to the game.....it's all bull....has nothing to do with anything but ego, there are these things called knock sensors that will compensate for fuel value and they are calibrated for the lower octane fuel as a matter of course. MB and BMW and so forth expect you, as the average owner to not put premium in and have hence programmed the ECU for that. That's why if you 'chip' an ECU you MUST put premo in or that'll really screw things up. The car is dumbed down for the average driver/owner....it's true