Originally Posted by AlexTek
You change your spark plugs every 7,500 miles? :-/
Actually on this car you would be surprised. I logged data, specifically ignition timing targets and consistently at about 7500 miles of driving my ability to hit the maximum timing targets is off and generally is 1 to 2 degrees shy of maximum. The car relies on the plugs to read knock and pull timing. Dirty plugs at all interfere with this process and leads to timing being pulled much more easily.
On a car without ion sensing knock systems I agree but unfortunately our plugs are not just responsible for the spark and ignition which I agree is premature to replace at that mileage but the plugs act as the sensor, and specifically the electrodes which is the first thing to really get dirty.
I just like getting the maximum out of my engine at all times even if it is only 10 hp more.