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Every time you pull up to a gas pump in the U.S., you'll likely be asked to select your fuel grade: regular, plus or premium. These different types of gas have different octane ratings—a measurement of how stable the fuel is. Most of us click “regular" for the lowest-priced fuel and move on with our day, but you might wonder, “Which type of gas is actually best for my car?"
The answer lies in your owner's manual, which always recommends the fuel grade that's best for your car. Most vehicles run just fine on regular fuel, but if you have a high-performance engine that creates more pressure, you'll need plus or even premium fuel to help your engine run effectively and avoid engine knocking.
What Are Octane Ratings?
At most pumps, there are three different types of gas available. Each has its own octane rating. Those are displayed as numbers on gasoline pumps and are a measure of the fuel's stability.
- Regular gas typically has an octane rating of 87.
- Mid-grade (often labeled “plus") has an octane rating of 88 to 90.
- Premium fuel has a rating of 91 to 94.
Understanding Different Types of Gas
To understand the differences between these types of gas, it's important to first learn how gasoline functions within your engine.
Internal combustion engines generate power through a process called combustion. In gasoline engines, a spark plug ignites a mixture of fuel and air inside the engine cylinders, creating controlled explosions (aka combustion). These explosions push the pistons up and down, transferring energy to the crankshaft, which propels the vehicle forward. Engines run most efficiently when combustion is controlled and happens with precise timing to keep your engine running smoothly.
However, engines can experience spontaneous combustion, also known as "pre-ignition" or "engine knock." This occurs when pressure and heat in the cylinder cause the fuel to ignite prematurely, without a spark. Engine knock produces a pinging or knocking sound due to uneven combustion. Over time, this can damage the engine, reduce power and decrease fuel efficiency. Fortunately, many modern engines are equipped with knock sensors that adjust timing to minimize these risks.
How Do Different Types of Gas Impact Your Engine?
The higher the octane rating, the more stable the fuel—which means you're less likely to experience engine knocking. Regular gas will spontaneously combust at a lower pressure than mid-grade or premium fuel.
Rarely, you might see fuel with an octane rating of 85. This option is only suitable for older vehicles with a carbureted engine or if you are living at a high altitude, where the atmospheric pressure is lower. Unless you're certain that an octane level of 85 is OK for your vehicle, it's best to avoid it.
Does Higher Octane Mean More Benefits?
You should always use at least the octane level recommended in your owner's manual. Beyond that, using higher octane fuel in a vehicle designed for regular gas provides minimal benefits, but there are a few potential advantages:
- Slight reduction in emissions
- Small increase in fuel economy
These benefits are most noticeable when the engine is working very hard, doing tasks like towing or driving in hot weather. However, for most vehicles, these benefits are minor and don't offset the higher cost of premium fuel. Unless your car's engine is designed to require or benefit from higher octane fuel, sticking with the recommended octane level is the most cost-effective choice.
So, Which Type of Gas Is Right for Your Car?
The easiest way to determine the right fuel for your car is to check your owner's manual, which lists the recommended fuel type. Most vehicles run just fine with regular fuel. Their engines are designed to run on gasoline with an octane rating of 87, so there is very little benefit to using a higher octane fuel in these engines.
However, some cars require mid-grade or premium fuel that can withstand higher pressure. This is most common in high-performance engines, including those in vehicles with turbochargers or superchargers. Since these engines create more pressure, they need greater fuel stability to avoid engine knocking.
If your manual specifies mid-grade or premium fuel, stick with it. Using lower octane fuel can cause engine knocking, which can damage your engine over time. Some modern engines adjust spark timing to prevent knocking, so you might not hear the telltale knocking noise, but you'll still experience reduced fuel economy and engine performance.
Using a Gas Card To Save
Higher octane fuel is more expensive to produce, so it costs more at the pump. But no matter what type of gas is right for your car, filling your tank can add up quickly. If you need plus or premium fuel, this may not be the best place to cut costs, as using a lower octane fuel than recommended by your manufacturer could lead to long-term engine damage. One way to offset the cost of fuel is by using a gas card. Many fuel loyalty programs offer discounts by the gallon when you fill up at a specific brand's stations. Additionally, some credit cards offer cash back on gas purchases, regardless of the brand. Depending on the program, these savings can help reduce fuel costs, making it easier to afford the grade of gas your vehicle requires.
Keep Your Car Running Smoothly
Choosing the right type of gas helps your engine run smoothly and helps prevent potential damage. Most cars are designed to use regular gas (87 octane), but it's always a good idea to check your owner's manual for the recommended fuel type. If you've been running on a lower octane than required for multiple gas tank fills, contact your mechanic to check for damage.
Remember, there's little advantage to putting higher octane fuel in your vehicle if it's not required. Engines designed for regular gas don't benefit from premium or super fuel, and the added cost will only make your trips to the pump more expensive. Stick to the fuel your car was designed for to keep it running at its best.
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READ MORE: 13 Tips To Help You Save Money on Gas
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