well, it may be more usable for engines that have higher baseline compression.. if you are using low rating gas that is prone to pre-ignition, or ping/detonation, the computer will retard the timing and instead of the expanding gasses pushing the piston they get wasted as heat out the exhaust, which would decrease the fuel economy by a certain amount for the time that the computer is acting on the timing... going up a long hill with 87 in a car that says use 91+ could possibly cause the exhaust gasses temperature to skyrocket and damage the valve seats, or overheat the head and blow a head gasket..Originally Posted by TurcoLoco
Oh, I knew you were aware, never in my mind I had a doubt!
Well, anyhow, to your question, the price difference leads believe to think that higher the rating the better the gas...
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