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Gas Grades, Octane and Your Car

Service station pump

Pull up to a service station pump and you’ll typically be confronted with three gasoline choices: regular, midgrade and premium. Each of the gas grades represents octane levels, which impacts your car’s performance. Choosing the right grade for your car means following the manufacturer’s requirements, your budget and reaping the benefits of choosing a preferred grade.

Octane Defined

Gas grades are determined by octane levels. Usually, those ratings are 86 or 87 for regular grade, 89 for midgrade and 91 to 93 for premium grade.

Gasoline’s octane rating is a measurement of fuel’s ability to resist knock or the shock waves that begin in the combustion chamber and vibrate the entire engine. In some cases, knock can damage valves and pistons.

What Your Manufacturer Says

Performance models such as this Subaru WRX require premium gasoline.Purchase a car and you should familiarize yourself with the owner’s manual. This is critical if the car is still under warranty. You need to operate the vehicle in such a way as to refrain from voiding the warranty.

The manufacturer explicitly outlines what type of fuel your car requires. Pay attention to two key words — “recommended” and “required.”

If a certain fuel is recommended, that’s the gas grade you should choose to optimize fuel economy and performance. Usually, the recommended level is regular grade and you could also choose to select any grade above it.

If a specific fuel is required, then you must choose that grade. You’ll find such a requirement for high-performance engines where premium fuel is necessary to optimize its operation. Select a lower grade and you may damage the engine and thereby void the warranty. Such engines are designed to burn gasoline at higher pressures and temperatures, and need premium fuel to operate under harsh conditions, such as during hard acceleration.

Performance and Your Budget

For owners who have latitude in their preferred gas grade, choosing a higher grade may come down to budget: paying an extra 10 to 50 cents per gallon for higher octane fuel. At the same time, there may be no benefit in choosing a higher grade, especially if performance remains the same.

Instead of spending money on an expensive fuel type with no real benefit, employ those funds for what matters — oil changes, coolant flushes, brakes and other maintenance due items.

If you desire to squeeze more power from your car, consider such upgrades as an exhaust system kit for improved acceleration and fuel economy and a sweeter exhaust note. Other upgrades include high-performance headers or an enhanced intake manifold.

Your Gasoline Brand

Finally, there is another factor in choosing gasoline — the brand. Like the majority of consumers, you might have endured years of hype from oil companies claiming their fuel is superior. There is truth in such pronouncements after all.

It turns out that so-called “top tier” gasoline is preferable for your car. Developed in 2004, top tier gasoline provides superior detergents to reduce engine carbon buildup and deposits in addition to burning cleaner and improving fuel economy.

Automakers such a Toyota, General Motors and Volkswagen back fuels produced by retailers including BP, Exxon-Mobil and Shell. You’ll pay a bit more for such gas — typically three cents per gallon according to Consumer Reports — but the long-term benefit may extend the life of your engine.

So, what’s the bottom line? Choose the right gasoline for your car and along with your usual care, you’ll ensure it runs optimally.

Check out all the fuel & emission system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on gas grades, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Matthew Keegan.

Matthew C. Keegan View All

Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.

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