Save your money. If your owner’s manual recommends regular unleaded, then that’s perfectly fine. You’re just wasting precious pennies if you pay for a higher octane fuel. Most of today’s cars, with the exception of high-performance engines, are tuned to run on regular unleaded fuel with little advantage to be gained by using premium. Here’s the skinny:

Your engine’s cylinders hold a mixture of gas and air. The cylinder compresses that mixture very quickly and your spark plug ignites it. That little explosion (like a cannon firing) is the combustion in an “internal combustion engine” and creates the energy to make your car go. The octane of a gasoline tells you how much compression it can stand before it ignites spontaneously. The higher the octane, the higher the compression it can take.

Most cars have an 8:1 compression ratio, which is perfect for regular unleaded gas. That means the cylinder is compressing the gas/air mixture at just the right rate.

If the gas isn’t a high-enough grade for the compression rate of the cylinder, it’ll ignite early, before the spark from the spark plug. And that’s bad for your engine. Those early explosions result in knocking and pinging. So, if you don’t hear any knocking and pinging, you’re using the right grade of gas. If you do hear those sounds, try upgrading to a premium gas. But, for most cars, using a premium gas doesn’t give you or your engine any advantage.