If you’ve ever pulled up to a gas station and hesitated between Regular, Midgrade, and Premium fuel, you’re not alone. Many drivers wonder which one is best, whether premium is worth the extra money, and what 87, 89, 91 actually mean. Choosing the right gasoline matters more than you might think. It affects your vehicle’s performance, fuel efficiency, and long-term engine health.
This guide breaks down everything you need to know about octane ratings, the differences between fuel grades, and how to select the correct gas for your vehicle.
What Is an Octane Rating?
An octane rating measures a fuel’s ability to resist engine knocking, which happens when gasoline ignites prematurely inside the engine’s combustion chamber. Knocking (also called pinging) reduces engine efficiency and can damage internal components over time.
The number you see at the pump, 87, 89, 91, or 93 is the Anti-Knock Index (AKI). This is a standardized measurement used nationwide and displays the fuel’s resistance to early ignition.
The higher the octane rating:
Understanding octane ratings ensures you aren’t overspending on fuel your car can’t benefit from or using fuel that could harm your engine.
Regular Gasoline
Regular gasoline with an 87 octane rating is the most commonly recommended fuel for the majority of cars on American roads. This grade is engineered for standard engines with moderate compression ratios, offering reliable performance at the lowest price.
Vehicles built for everyday commuting, compact cars, sedans, crossover SUVs, and many light trucks, are optimized to run efficiently on regular unleaded fuel. Using higher octane fuel in these vehicles will not improve horsepower or fuel economy. Instead, regular gas ensures smooth operation, predictable performance, and affordable refueling costs.
Midgrade Gasoline
Midgrade gasoline, often labeled 89 or 90 octane, offers slightly higher resistance to engine knock compared to regular. In the United States, midgrade is sometimes recommended for vehicles with engines designed to operate at slightly higher compression levels or for drivers looking for improved performance during heavy loads, like towing or driving in mountainous terrain.
Some manufacturers list midgrade as “recommended” for optimal efficiency and power output. While not as widely required as premium fuel, midgrade can be a beneficial middle option for drivers who want smoother acceleration or are operating older engines that may benefit from more controlled combustion.
Premium Gasoline
Premium gasoline typically ranges from 91 to 94 octane, depending on the state and station. This fuel grade provides the strongest resistance to knocking, making it essential for:
Manufacturers design these engines to operate at higher pressures and temperatures, requiring a stable, knock-resistant fuel. When used in the proper engine, premium gasoline can enhance throttle response, preserve engine power, and maintain optimal fuel efficiency.
While premium fuel is more expensive, it’s necessary for protecting the engine and maintaining performance.
What Vehicles Need Premium Gas?
Vehicles that require premium gasoline include many high-performance brands such as BMW, Audi, Mercedes-Benz AMG models, Lexus F-Sport models, Porsche, Cadillac V-Series vehicles, and turbocharged models from various manufacturers.
If your car requires premium, you’ll see wording such as: “Premium Fuel Only,” “Use 91 Octane or Higher,” or “Premium Recommended.”
Using the correct fuel prevents knock, protects the precision components inside performance engines, and ensures the car delivers its intended power and efficiency.
Which Octane Fuel Should You Use?
The safest and most accurate way to determine which fuel your vehicle needs is to consult the owner’s manual or fuel door label. U.S. vehicles are very clear about required octane ratings. If you no longer have a physical manual, you can find a digital version on the manufacturer’s official website.
Follow these guidelines:
-
If your car requires 87 octane, use regular.
-
If your car recommends 89 or 91, you can still use 87, but the engine may not perform at its best.
-
If your car requires 91 or 93, always use premium. Running on lower octane can cause damage.
Can You Use Premium Gas If Your Vehicle Only Needs Regular?
Yes, you can, but it won’t do anything for your vehicle. Engines designed for 87 octane cannot take advantage of the properties of premium fuel. Using higher octane will not improve horsepower, fuel economy or clean the engine better.
In most cases, using premium in a regular-grade engine simply costs more without offering any benefit.
Can You Use Regular Gas If Your Vehicle Requires Premium?
Never use regular gasoline in a vehicle that requires premium. Although the car may still run, doing so can lead to:
-
Persistent engine knocking
-
Reduced power and slow acceleration
-
Decreased fuel efficiency
-
Potential long-term engine damage
-
Warranty issues
High-performance engines are precisely calibrated, and using the wrong fuel can cause expensive problems over time.
What If the Manufacturer Says Premium Is “Recommended”?
If your vehicle states “premium recommended,” it means the engine can run on regular gasoline, but you may notice reduced performance or fuel efficiency. Using premium ensures the engine operates at its intended power level, giving you stronger acceleration and smoother driving, especially in demanding conditions.
Drivers who want the best performance and longevity from their vehicle typically choose premium in this scenario.
Benefits of Using the Correct Gasoline for Your Vehicle
Using the appropriate octane rating offers several long-term benefits:
-
Improved combustion efficiency
-
Higher or more consistent fuel economy
-
Optimized engine performance
-
Reduced likelihood of knocking or misfires
-
Better overall engine health
-
Lower maintenance and repair costs
Choosing the correct fuel protects your investment and keeps your vehicle performing the way the manufacturer intended.
What Happens If You Use the Wrong Octane Fuel?
Using the wrong octane rating can cause a variety of problems depending on your engine’s design and how frequently the wrong fuel is used. Consistently ignoring your manufacturer’s fuel recommendation can lead to the following issues.
Using lower-octane fuel than required often results in engine knocking, where the air–fuel mixture ignites before the spark plug fires. This premature ignition causes a knocking or pinging sound and can interfere with smooth engine operation. Over time, this puts stress on the pistons, valves, and spark plugs, potentially causing mechanical damage that can lead to expensive repairs.
In addition to mechanical stress, engines designed to run on higher octane fuel may lose performance when using a lower grade. You may notice weaker acceleration, delayed throttle response, and an overall reduction in power because the engine’s timing and fuel delivery systems cannot function at their intended levels. To prevent knocking, the engine detunes itself, operating less aggressively and less efficiently.
Fuel efficiency may also suffer. Even though many modern engines can adjust to lower octane fuel using knock sensors, this adjustment typically involves reducing power output and altering ignition timing, which leads to increased fuel consumption. Over time, what seems like a cost-saving decision at the pump may end up costing more in fuel usage.
In more severe cases, using the wrong octane can trigger the check engine light, signaling that the onboard diagnostics system is detecting irregular combustion or abnormal sensor readings. This can require diagnostic testing and additional maintenance to resolve.
How to Avoid These Issues
To avoid these complications, always use the octane level specified by your vehicle’s manufacturer. You can find this information in your owner’s manual, on a label inside the fuel door, or on the automaker’s website. Following this recommendation ensures your engine operates properly, stays efficient, and avoids unnecessary repairs.
Save Money by Using the Right Gas and Car Insurance
Choosing the correct fuel protects your engine, saves you money on maintenance, and keeps fuel costs predictable. Pairing that with the right car insurance can help you reduce overall vehicle ownership expenses. We offer affordable full coverage insurance plans for all drivers. Call us today to get a quote and start saving money.