Octane rating is a measure of a fuels resistance to pre-ignition( detonation or, if you like, making like a diesel)
Regular Otto cycle gasoline engines are not built to be diesels, they are built to burn a gas/air mixture not explode it. The knock sensors in engines "listen" for a particular set of sounds and then retard the ignition ( detune the engine) until these sounds go away... then they allow some ignition advance until it comes back and so on. So as Artic has pointed out ( very patiently, many times in many threads) if the knock sensors are doing their job with fuels of too low a grade the piston tops are being continually pounded by detonation... in the short term most modern engines will survive this but it will not help the life of pistons, rings, rod bearings etc.
In the specific case of forced induction engines, instead of the mixture being sucked into the engine it is being blown into he engine and some proportion of the engines compression stroke is already done....so the mixture is closer to detonation anyay... its usually hotter as well intercooler not withstanding.
So you need fuel with a higher anti-Knock index or octane rating. One excellent additive is ethanol hence the preference around here for Sunoco 94 in turbo engines. Lead compounds are another but no longer allowed etcetera.
Low Rpms are not necessarily safe. The engines need for octane is highest at the torque peak which is just where granny's automatic transmission will run the engine under acceleration.
maybe we need a new forum section called:
"The same old questions discussion"
it could cover regular gas, oil changes and syn oil, the desirability of winter tires and ( sorry Barrie) the inevitability of putting a small block in every road vehicle on the planet.
