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 can — and should — involve a lot of research, which may reveal that the vehicle you want requires premium fuel. That might be disappointing, since premium gas often costs an additional 80 cents or more per gallon than regular. With the nationwide average price for premium hovering around $3.80 per gallon in December 2025, according to AAA, a 15-gallon tank of high-octane gas cost $57. That’s $12 more than filling up with regular unleaded at that month’s average price, 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?
Determining whether you need to use premium fuel begins with understanding 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.
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, but were instead 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.
Can You Put Premium Gas in Any Car?
Since premium fuel prevents engine knocking, why don’t all cars use 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 want to cut costs at the gas station, don’t pay extra for premium unless your vehicle actually needs it,” said Autotrader Senior Advice Editor Chris Hardesty. “Check your owner’s manual to see whether premium fuel is required or just ‘recommended.’ And remember: Cars that require premium deliver their best performance — and their best fuel economy — when you use the specified 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 mistake.
MORE: What Happens if You Overfill Your Gas Tank?
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 primary issues that can result from skipping premium fuel is a loss of performance. Specifically, you may notice that the car runs more slowly when using 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 specifies that premium fuel is required, use it. But your car won’t blow up if you occasionally opt for regular.
MORE: Should You Get Your Oil Changes at a Dealership?
Which Vehicles Need High-Octane Gas?
Using lower-grade fuel in automobiles that require premium gasoline may reduce performance and lead to costly repairs later. Generally, vehicles with high-performance engines require high-octane gas. Older cars with engines that begin to “knock” or “ping” might also 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.
Editor’s Note: This article has been updated since its initial publication. Doug DeMuro contributed to the report.
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.
HERE’S A TRICK: My car knocked and hesitated with Regular gas. But my 20 gallon fuel tank costs almost $9 more to fill with Premium at my local gas station. I stopped that nonsense. Instead I bought some STP Octane Booster from Amazon: I bought a dozen for $3. each. Car runs great, knock is gone, car jumps up hills and the detergent additive is a bonus.
I had a BMW Z3 that allowed for either, the BMW X1 I had for example required premium 89 or higher. If you don’t use it when it’s required you can cause dirty injectors for turbos etc..
My current car, INFINITI G37, stuffers from pre-ignition on hot start if I use low octane so I only use premium.
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