I think you are both right. It is basically a steady-state argument, wherein an infinitely slow burn would wield the maximum effiency or total energy. However, it depends entirely on the way the car is tuned, or is capable of tuning itself. As mentioned, the timing can be advanced further to completely burn the higher octane fuel without detonation. However, I have heard of incomplete burning of higher octane in cars that cannot advance timing. So it all depends on the car - it has to have the ability to learn to maximize the fuel or to be tuned for it.Originally Posted by drummerboy
To the OP, I have driven 1.5 years on the 91 and 1.5 years on the 93. The 93 is noticably better for our cars. I would cringe to think I had to put in 91 again. I like my advance ignition multiplier where it is, and l like life without any pinging.