Did I just read the GTP requires Hi-Test ?? I'm about to purchase a pristine '99
For optimum performance and fuel mileage high test is recommended. You can use regular but don't do any high performance driving or you could blow a hole in the pistons. I'd say bite the bullet and use premium.
Try both grades and use the type that gives you the best miles per gallon.
No, do not choose your fuel for miles per gallon! That's not what its for. Use the fuel recommended by the manufacturer, which in the case of the GTP is midgrade or premium. Check the owner's manual for your specific application to be sure. The correct fuel helps the engine operate at the corrrect temperature and that is necessary for the overall health of your engine.
Low grade fuel in a forced induction engine or an engine with a high compression ratio will cause predetonation. Predetonation can bend rods if it detonates early enough.
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