Premium gas vs. regular: Which is best for your car?

What is premium gas?

Premium gas is a 91-octane gasoline designed to fuel high-performance engines. A higher-octane rating means the fuel is better balanced and stabilized against spontaneous combustion, which can cause knocking and damage to a car engine. Premium gas may also contain additional, higher-quality additives compared to regular gas. However, premium gas might not be necessary or improve efficiency for cars that are designed to run on regular gas.

What is regular gas?

Regular gas is an 87-octane fuel. Octane ratings measure fuel stability. The higher the octane number, the more stable the fuel. Most cars on the road run on regular gas.

Does higher octane gas last longer?

No, any fuel efficiency gained using premium fuel would stem from engine performance, not the gas itself. Buying premium gas won't have you visiting a gas station any less frequently, especially with a standard engine not designed to take advantage of premium gas.

Does premium gas give better gas mileage?

Premium gas can increase fuel efficiency, potentially giving better gas mileage for longer while decreasing emissions, if you have a car designed to run on premium gas. Also, premium gas is more resistant to engine knock in luxury and performance vehicles with turbochargers or high-compression engines, so you can hit that horsepower smoothly.

Remember that you see these benefits only in vehicles requiring premium gas and not necessarily in most other vehicles. Check your owner's manual to see which gas type your manufacturer recommends for your specific car make and model. Note that the definition/label for premium gas can differ from state to state and station to station.

Some of the various names for automotive fuel with high octane levels of 91-94 include:

• Premium
• Super Premium
• Ultra
• Ultimate

Should I use regular or premium gas?

You should use the type of fuel the vehicle's manufacturer recommends. A vehicle that runs on regular gas will not run any better on premium fuel. Using premium gas in a vehicle designed for premium gas will help the car perform better and avoid damaging the engine with regular gas.

What cars require premium gas?

Cars that require premium gas to operate safely will have an indication inside the fuel filler door and in the car's manual. The indication will typically specify the minimum octane rating necessary, which can be important if you have multiple premium options to choose from. Some cars that need premium need at least 91 octane, and others may require at least 93 octane.

If the owner's manual recommends premium gas instead of requiring it, you can typically operate the vehicle safely on regular gas. Still, you may not reach the performance and fuel economy indicated in the car's specifications. In most cases, the difference in performance is small and something you may not notice during normal driving.

If the car is designed for regular gas — or doesn't specifically say that the car requires premium gas — go with regular. There are no benefits to putting premium gas in a car that doesn't need it.

What happens if you use premium gas instead of regular?

The only thing that will happen if you use premium gas in an engine designed for regular fuel is that you'll spend more money, according to Cars.com. An engine that runs on regular gas will not perform better because you put premium gas in the tank. If you fill up on premium because the engine knocks when you use regular, your car might need a mechanic.

Find out what to do if you use the wrong gasoline.