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Because the engine is designed to run on Regular Unleaded. You are wasting your money running a higher octane fuel. It is a myth that higher octane fuel creates more power or more mpg. Octane has nothing to do with power nor MPG. Anyone who tells you different does not know what they are talking about. Octane is used to prevent pre-ignition in a high compression engine and nothing else. This is why people think it increases power. They assume that performance cars use Premium so it must increase power. Absolutely not the case. High performance engines use premium due to their high compression rations. Use the octane fuel recommended by the manufacture. Running a higher octane can actually damage some engines.

2006-08-30 23:34:26
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Q: Your 98 grand prix runs poorley on premium gas engine light comes on and is hard to start however all symptoms cease and car purs on regular unleaded WHY?
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