Premium gas sounds fancy, and we all want cleaner, more efficient engines in our cars. But is that what you’re getting when you go for premium at the pump?
Who hasn’t wondered as they fill up on regular unleaded, “Should I be buying premium instead?” What might I be missing out on? Better gas mileage? A longer lasting engine? A better job? A nicer house? A loving family complete with spouse, 2.5 children, and a small-to-medium size dog?
To answer these questions, or at least the ones pertaining to cars, we’ve got to dig into the common assumptions people have about premium gas. It may not come as a surprise, but the “premium” labeling on the pump is basically marketing spin on a difference in octane. Some cars are built with lower octane fuel in mind while others are tuned to run on higher-octane fuel. Premium fuel doesn’t automatically make a car run better, cleaner, or more efficiently. In most cases, running on premium fuel is just a waste of money, and here’s why.
For us in the US, we’re used to typically three different octane numbers on our gas pumps: 87 for regular, 89 for plus, and 93 for premium. Octane refers to a gas’ resistance to pre-ignition or knocking. The higher the octane number the greater the resistance to knocking. In some cases, especially in engines with a higher compression ratio, the air-fuel mixture can ignite prior to the spark, leading to what’s known as engine knock. Obviously, uncontrolled explosions aren’t good for your engine so avoiding knock is pretty important.
Today’s engines have a knock sensor that can listen for any pre-ignition explosions and the computer will adjust timing to compensate. For some vehicles, like heavy-duty trucks or performance cars, they’re engineered with higher compression in mind and therefore run best on higher-octane fuel. This is particularly the case in vehicles with turbochargers or superchargers that increase engine compression.
But what about detergents/additives? Detergents in gas help remove carbon and “gunk” built up on engine parts. The EPA has stipulated a minimum amount of detergents that all gasoline blends are required to have. While there are differences in the amount detergents a fuel blend has (above the legal minimum), the amount of detergents aren’t necessarily related to the “premium” label you’re seeing at the gas station. Many brands of gas put the same amount of detergents in each of their blends while others, like Shell for example, put more additives in their premium fuel.
This doesn’t mean you should be running out to buy Shell premium gas for your non-premium car. For the most part, you’d be paying more for next to nothing in terms of performance. In fact, AAA estimates that Americans spend upwards of $2 billion dollars on premium fuel their cars don’t need.
In reality, you should be putting in your tank exactly what your owner’s manual says. If your car calls for 87 octane, use that and sleep well at night knowing your frugality didn’t come at any expense to your car’s performance. And if your vehicle calls for premium, buy premium because that’s what your car was engineered to run on.
The real conundrum is, what about cars that say premium fuel is recommended but not required? In this case, you can eke out minor benefits by running premium fuel. Using premium in these vehicles can improve fuel economy and power output, but the differences are typically marginal at best and don’t make up for the extra expense of buying premium fuel. Thanks to your vehicle’s knock sensor, the computer should prevent any knocking with regular unleaded. If you do happen to hear a knock with your “premium recommended” vehicle, by all means run premium as a precaution.
At the end of the day, the premium gas is for performance vehicles and unless your owner’s manual specifically calls for it, save your money and stick with regular unleaded.