What's the difference between gas grades?

October 04 2018


Have you ever pulled into the gas station and wondered why there are so many fuel options? Find out the difference between regular unleaded, midgrade and premium. 

It's all in the octane.

Octane refers to the volatility of the fuel. The lower the number, the more easily the fuel burns. On average, regular unleaded fuel rates an 87, midgrade (or plus) fuel rates an 89, and premium rates a 92.

Which one should you use? 

Most vehicles are designed to run on regular gasoline. In fact, 83 percent of purchased gas is regular grade. But engine design dictates what type of fuel you'll need. Here are some general guidelines when it comes to gas grades: 

  • Low-grade fuel combusts more easily than premium so it could cause knock -- or detonation, which could be a symptom of an incorrect balance of fuel and air -- in some engines.

  • Depending on the cause, excess knock might be eliminated by upgrading to higher grade gasoline.

  • Upgrading to a higher octane level has no benefits if your vehicle doesn't need it. Actually, using a too-high octane fuel can damage your car's emission system.

  • If your car requires premium, the manufacturer will make sure that's clearly stated.

What about diesel? 

Never use diesel fuel in a gasoline engine or vice versa. In a gasoline engine, spark plugs ignite the fuel, whereas diesel engines have no spark plugs. They run using compression ignition. Since gas engines aren't designed to handle this type of combustion, filling up with diesel could cause damage. 

Check the manufacturer's recommendation.

To help keep your car running smoothly and your engine in good shape, always go with the grade suggested by the manufacturer. Get in touch if you have questions about the type of fuel you should be using.

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