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Low compression engines run lower octane fuel[burns quicker]. High compression engines need higher octane fuels[burns slower] so you don't get premature ignition[fuel ignites before reaching top dead center] similar to a diesel,which causes detonation[pinging]. A turbo kinda has both situations,it is a low compression engine[fairly mild mannerd] until the exhaust gases start spinning the turbine and create boost,then the engine becomes a very high compression engine and at that time needs high octane fuel,especially while you have your foot in it. If you drove very easy and never needed the engine to perform under boost, I can see how the car could run good or better on regular gas. That's why there's absolutely little or no benefit to running high test in a car that doesn't call for it. High octane gas doesn't turn maw and paws Buick Century into a high performance machine !