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Do not buy gasoline of a higher octane than your car's owners manual recommends. It is just a waste of your money and chemicals used to increase the octane of the gasoline.
Octane rating has nothing to do with the energy or power in the gasoline. It is strictly a rating of the resistance of the gasoline to knock (premature ignition). A high-performance engine with high compression generally requires higher octane gasoline. I race a Turbo Porsche and it requires gasoline with an octane rating of about 100 to resist knock.
For most cars, an octane rating in the upper 80's is adequate. If your car does knock on the gasoline with the required octane rating, then either something is wrong with the engine or the gasoline is actually a lower octane than stated. Try a different gas station first. If your engine still knocks, have it serviced.