Rock Talk

Everything You Need to Know About Using Different Gas Grades

Last updated on May 16th, 2017 at 02:40 pm

When many people pull up to the pump it’s usually, “Fill ‘er up with regular.” What about using different gas grades? With gas prices on the low side, have you ever wondered if you should treat your car to a tank of premium gas?

What Gas Grade Numbers Mean

Pull up to any pump and you’re immediately asked to select one of the yellow octane rating stickers required by the Federal Trade Commission. Stations vary in the terms they use. You might see:

Regular/Unleaded: 85 – 87 minimum octane rating

Mid-Grade/Plus/Silver: 87 – 89 minimum octane rating

Super/Supreme/Super+/Premium/Ultimate: 91 – 93 minimum octane rating

The octane rating of gasoline refers to the performance, or compression ratio, of your car’s engine. It tells you how much the air-fuel mixture can be compressed before it will spontaneously ignite. It’s a measurement of how much pressure your car’s engine must exert on the fuel. A higher octane number allows the fuel to tolerate more compression before igniting. Put another way: high-octane fuel burns more slowly.

Does My Car Need High-Octane Gas?

Check your owner’s manual to determine your specific car model’s requirements. Edmunds points out the difference between a car manufacturer that “recommends” high-octane gas and one that “requires” it. According to the FTC, research indicates “drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.” Most cars run fine on regular octane fuel. Still, check your owner’s manual for any specific recommendations or requirements.

There are, however, some luxury and sports cars that do need mid-grade or premium gasoline. If you’re driving a high-performance BMW or Mercedes that requires high-octane fuel and you give it low-octane gas, you could run the risk of damaging your engine.

High-performance engines that require premium gas, but are filled repeatedly with regular can result in elevated exhaust-gas temperatures and a very noticeable rattling or pinging noise called “engine knock.” This is caused by the premature ignition of the compressed fuel-air mixture in one or more cylinders. While the occasional light knocking won’t harm your engine, a loud and persistent knock can lead to engine damage.

Plymouth Rock Assurance has other do-it-yourself car care tips to keep your ride in top-notch condition without spending a lot of money. Regular maintenance could even help you save big in the long run.

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