octane rating is just a fuel's resistance to detonation.....a car meant to run on 87 octane will run best on just that,87 octane...not only will putting high test in the car be a waste of money, you will actually LOSE power,granted only VERY slightly
There is nothing in our ECU's that will sense 89,91,93 octane or whatever and say "hey, it's ok to advance ignition timing" and adjust for the higher test fuel...if this was so,it would create more power, and we would all be using high test for a horsepower gain
the only thing in the car like this is a knock sensor..this is basically a glorified microphone tuned in to detect the sounds of knock from pre-ignition...if it does, it sends a signal to the ECU to RETARD timing....so basically the only way a situation would happen the way YOU stated, it would still be just a misinterpretation
like this: you start hearing rod knock running 87....to fix it you run 89 and this temporarily gets rid of it...but guess what...the fuel was the problem, something ELSE was and you just covered it up...then it gets worse...knock comes back...then you switch to 93..knock goes away again...YOU interpret it as the ECU getting USED to the fuel, when in fact you couldnt be more wrong........
make sense ?????
