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Grades of Gas: What’s the Difference?


Unless your car uses some sort of alternative fuel such as the ones noted here, you’re likely to fill up your car’s tank fairly regularly. When you do, do you ever ask yourself why are there different options available for your gasoline?

What’s in a Name?

Many gas stations name their grades of gas with fancy names. You may have seen “Plus”, “Super”, “Premium”, “Ultimate”, and more. However, these are nothing more than a way to coerce you to choose the more expensive choice when you might not benefit from it at all. The more important names to notice are “Unleaded” vs “Diesel” vs “Ethanol”. Unleaded refers to regular gasoline (leaded gasoline was phased out decades ago). As the owner of a vehicle, you need to know what type of fuel your car drinks. This is just as important as not feeding chocolate to your dog. Your vehicle will say which type of fuel it requires generally on the fuel filler cap, and sometimes on the gauge cluster.

Premium Gasoline

What’s in a Number?

If you’ve figured out your vehicle takes unleaded gasoline, now you should decide between an array of values which usually range from 87 to 93. Generally, the higher the number, the more expensive the fuel. What do the higher numbers mean? The number refers to the octane rating of the fuel. The octane rating reflects the resistance of the fuel to detonation. Detonation refers to a fuel igniting without a spark due to high compression and heat. The higher the octane rating, the more resistant to detonation the fuel is. Detonation is dangerous to gasoline engines because the fuel is igniting before it is supposed to, pushing the vehicle’s pistons backward, and can eventually lead to engine failure. To learn more about octane, see the article on fueleconomy.gov.


So, which one do I choose?

If your vehicle only specifies to use unleaded fuel, you may choose any of the unleaded choices and can choose the cheapest of those options. You won’t necessarily see any gain from using the (more expensive) higher octane fuels, so you’ll likely be spending more money for literally no gains. If you live in a high-altitude area you might see 85 as an option, but 87 octane is a recommended minimum (unless you have a 30-year-old vehicle with a carbureted engine).

If your vehicle specifies “premium only,” look to purchase the premium fuel to avoid detonation and potential damage to your engine. Generally, vehicles from Audi, BMW, and Lexus specify ‘premium only’ and have high compression ratios or turbocharged engines that require the higher octane to prevent detonation.

What can I save?

Premium fuel comes at a premium price. Considering the average car travels 12,000 miles per year and gets about 25 miles per gallon (and most cars get the same mileage on either type of fuel), we can deduce that the car uses 480 gallons per year. Using regular 87 octane ($2.29 as of this writing) would cost $1099.20. Using premium ($2.78 as of this writing) would cost $1334.40. Thus, using regular saves you $235.20 a year (or $0.64 per day) over premium.

Looking to save even more money? Check out Driving Tips to Save Gas.

Hopefully this article clears up some of the haziness in your fueling future. It may also have added one more thing to look for when deciding on a new vehicle: fuel type and cost. Speaking of, find your next ride on Carsforsale.com.

Caroline Rex

She's a graphic designer by trade, but loves writing blog posts on the side. As a closet car fanatic, Caroline enjoy sprinkling knowledge about the unique ins and outs of the underdogs of the auto world. #neonsruletheworld

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