The benefits of premium gas can be difficult to separate from the marketing hype that goes with it. Presented as the “top tier” fuel at your local filling station, it can often seem like a question of “good, better, best” when choosing which option to pump into your own tank.
The reality, however, is a little more complicated than that. There are very good reasons why you might want to pay more for premium gas, but most of them were mechanically predetermined long before you pulled in to fill up.
What’s That Knocking Sound?
The reason there’s more than one type of gasoline available is because car companies manufacture engines that require fuels with different resistance levels to “knock.” Knock is the sound an internal combustion engine makes when the fuel being compressed in the cylinder ignites before the spark plug has a chance to fire. This is called “detonation” or “preignition,” and it not only robs your vehicle of power, but it can also cause damage to numerous mechanical components.
The octane rating on a modern gas pump is actually a representation of its resistance to knock. In fact, one of the main benefits of premium gas is that it avoids detonation better than regular gas. The higher the octane — usually expressed as a range from 87 to 94 — the stronger the resistance.
Use As Directed
Engines that have a high-compression design or utilize a form of forced induction, which usually includes a turbocharger or a supercharger, often require high octane fuel to prevent preignition from becoming a problem when the vehicle is under load. If this is the case for your car, then the benefits of premium gas will be listed in the owner’s manual, and it is typically noted as a requirement on the sticker found inside the fuel door itself.
If your engine isn’t specifically designed to require 91, 93 or 94 octane fuel, however, you won’t see any difference running the more expensive gasoline in your car. It won’t improve fuel economy, allow your engine to burn “cleaner” or offer any other benefits. If a vehicle’s ECU isn’t programmed to advance timing and to take advantage of premium gas, it will burn just like the 87 octane that your vehicle was designed for — even if you use an aftermarket octane booster.
Premium gas is helpful to engines that need it, but wasted on those that don’t, so don’t feel pressured into paying for more octane.
Check out all the fuel and emission system parts available on NAPA Online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on the fuel you should use in your car, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.