Quick Facts About Using Premium Gas in Your Car
- Many drivers think high-octane fuel is more refined, cleaner, or otherwise “better” than regular gas, but it isn’t.
- Save money at the pump and only buy premium gas if your car requires it.
- Follow the guidance in your owner’s manual and use premium if the high-compression engine needs it for optimal performance.
Buying a car should involve a lot of research, and it could reveal that the vehicle you want requires premium fuel. You might face disappointment since premium gas often costs an additional 80 cents or more per gallon than regular. At today’s average price of $4.46 per gallon, a 15-gallon tank of high-octane gas costs $66.90. That’s $12 more than filling up with regular unleaded, and it could be a deal-breaker for some drivers.
Can you buy the car anyway and skip the premium gas? We have the answer.
What Is Premium Gas?
Discussing whether you need to use premium fuel begins with an overview of how premium fuel differs from regular gas.
Many drivers think premium fuel is more refined or cleaner than regular fuel, but that’s not true. It’s simply less combustible than regular gas. What exactly does that mean?
We’ll spare you the mechanical details of why you should or shouldn’t use premium gas. But the critical thing to remember is that engines running on less combustible fuel are less likely to experience pre-ignition than powertrains that run on more combustible regular gas. Pre-ignition leads to engine knocking. You can sometimes hear it in older cars or high-performance vehicles that require premium gas and instead were filled up with a tank of regular.
Too much engine knocking can cause damage. It means your engine isn’t running very well, which isn’t something you want to deal with after buying a car from a private seller or a dealership.
What Number Is Premium Gas?
Yellow stickers on gas pumps have numbers to indicate octane levels for gasoline. Premium gas has an octane level of 91 to 94. Regular unleaded is 87, and midgrade is 89.
Can You Put Premium Gas in Any Car?
Since premium fuel prevents engine knocking, why don’t all cars take premium? The answer lies in the engine’s construction.
A typical car doesn’t need a high-performance engine because it uses a simple design with a low compression ratio that runs fine on regular gas. However, most high-performance or luxury cars bring more power and a higher compression ratio, which means their engines are more prone to pre-ignition when using the wrong fuel type.
“If you’re looking to save money at the pump, make sure you’re not buying the pricier premium fuel for no reason,” says Autotrader Executive Editor Brian Moody. “Your owner’s manual should tell you whether you MUST use premium fuel or if it’s just ‘recommended.’ Keep in mind, cars that ‘require’ premium fuel perform best and get their best fuel economy when you stick with the required octane rating.”
Can You Mix Premium and Regular Gas?
You can mix regular gas with premium gas. However, adding regular to premium fuel already in the tank dilutes the overall octane level, which could cause engine performance loss on cars requiring premium gasoline. On the other hand, you can also bring up the octane level by adding premium grade after you realize you previously pumped regular gas by accident.
MORE: Should You Get Your Oil Changes at a Dealership?
Do You Have to Use Premium Fuel?
So you need to use premium fuel in a luxury car, right? Most luxury vehicles provide engine-knock sensors, meaning they won’t allow the engine to knock, even if you put in the wrong fuel type. Avoiding engine knock prevents engine damage, so your engine will likely run just fine even if you put in regular rather than premium.
Even if your engine isn’t knocking, regular fuel might still cause problems. One of the main issues that can come from skipping premium fuel is a loss in performance. Specifically, you might feel the car runs slower if you use regular fuel. You might also notice a drop in fuel economy since the engine probably isn’t running at its most efficient level, even though it isn’t knocking.
That brings us back to whether you must use premium gas. In many cases, you can get away with gassing up with regular fuel with no noticeable issues except for minor performance and gas mileage losses. But it’s not worth taking the risk.
Bottom line: If your owner’s manual says that premium fuel is required, you should use it. But your car won’t blow up if you occasionally opt for regular.
Which Vehicles Need High-Octane Gas?
Using lower-grade fuel in automobiles that require premium gas may reduce performance and cause costly repairs later. In general, vehicles with high-performance engines require high-octane gas. Also, older cars with engines that begin to “knock” or “ping” might benefit from a tank of premium gasoline. Remember, following the manufacturer’s fuel recommendation and keeping up with the maintenance schedule helps you retain its value when it’s time to trade or sell your car.
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Editor’s Note: This article has been updated since its initial publication.
I’m not sure anyone should follow my advice but I have a 2018 BMW X5 5.0 that ‘requires’ premium. I’ve never put premium in the car and have always used regular 87 octane. The car has 40,000 miles and I’ve never had an issue. Performance is excellent and I’m still faster than most cars on the road. I’ve never experienced any hesitation, lack in performance, etc.