Raising the octane rating (also known as the anti-knock index) doesn't change the energy content of a gallon of gasoline. A higher octane rating indicates greater resistance to knock, the early combustion of the fuel-air mixture that causes cylinder pressure to spike.

Does higher octane gas really make a difference?

In a consumer notice, the Federal Trade Commission, notes: “In most cases, using a higher-octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner.”

Is there really a difference in gas octane?

What is the difference in octane levels? Octane is how much compression a fuel can withstand before igniting, or rather it's a measurement of a fuel's ability to avoid knock. ... Typically “regular” gas is 87 octane, “midgrade” is 89 octane and over 91 octane is “premium” gasoline.