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What you'll learn in this article

  • What the numbers on the gas pump mean
  • What type of gas most cars need
  • What happens when you use the wrong gas
  • How gas powers your car… And more!

You probably see some variation of the same three options at every gas station in the United States: Regular, Plus, and Premium. Some stations even offer up to five variations. But what do those numbers mean on the pump? And how do you know which gasoline is best for your vehicle? In this article, we'll answer those questions and more, but first let’s explain a little about gas.

Gasoline and air combust in your engine.

In order to understand your fuel options and which is right for your vehicle, it helps to first understand how gasoline is used in your engine. Believe it or not, the way gas is used in your vehicle is something similar to miniature explosions.1 These “explosions” (also known as combustion) detonate a fuel and air mixture at just the right time when the pistons in your engine move up and down. The force of the combustion is transferred to the crankshaft2 to propel your vehicle forward.

Octane rating, that number you see on the pump, is the measure of a fuel's ability to resist "knocking" or "pinging" during combustion. This typically sounds like a clunking while you are driving. The "knocking" is caused by the air and fuel mixture detonating prematurely in the engine.

Those numbers on the pump represent octane levels.

Unleaded gasoline typically has octane ratings of 87 (Regular), 88–90 (Midgrade), and 91–94 (Premium). In some high elevation areas, you may find gasoline with an octane rating of 85. Ethanol has a much higher-octane rating of about 109.3 Ethanol has a higher-octane number than gasoline, which provides increased power and performance If your car is made for It.

The vast majority of automobiles require Regular (87), but Premium is crucial for engines with a higher compression ratio. While the lower rating of 85 is available in some places, this option is only suitable for older vehicles with a carbureted engine. Before selecting your gas Consult your owner’s manual for the vehicle manufacturer's octane requirements.

If you do happen fill up with the incorrect gasoline, most newer vehicles use electronic sensors adjust the spark timing to reduce the knock. An octane level that is too low can reduce the fuel efficiency of your vehicle.  If you are towing a heavy load, a higher-octane level may improve fuel efficiency and reduce carbon emissions but typically makes no difference in normal driving conditions. The Federal Trade Commission (FTC) says there are no advantages to using Premium gas in cars that do not require it.4

“It won't make your car perform better, go faster, get better mileage, or run cleaner,” the FTC states on their website. “Your best bet: listen to your owner's manual.”

Don’t let an empty tank slow you down. Use your Synchrony Car Care credit card at gas stations nationwide across all major gas brands. *

Find a Location


1. What do the different grades of gasoline mean? Policygenius.com

2. 4-Stroke Internal Combustion Engine NASA.gov

3. Selecting the Right Octane Fuel FuelEconomy.gov

4. Ethanol Benefits and Considerations Energy.gov

Paying a Premium for High Octane Gasoline? FTC.gov

Unleaded vs. Premium: What Is Really the Best Gas to Use? Auto.edu

* Subject to credit approval. Visit www.mysynchrony.com/carcare to find gas locations where Synchrony Car Care is accepted in the U.S., including Puerto Rico.


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