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Regular or Premium: Which Fuel Is Right for My Car?

Every time you go to the pump, you are faced with something of a dilemma—regular or premium? You want to pay less, of course, but is that going to cost you in the long run?

To find the right fuel for your car, you have to consider more than price.

Understanding the Difference in Fuel Grades

Most gas pumps in the US have three different grades—regular, midgrade and premium (sometimes call Ultra, Super Ultra, Super Premium or something similar). These grades are based on the gasoline’s octane rating, which indicates the maximum compression (and corresponding engine temperature) the fuel can withstand before igniting.

Typically:

  • The higher the octane, the higher compression ratio…
  • The higher the compression ratio, the higher the engine temperature…
  • The higher the engine temperature, the more efficiently the fuel burn…

And efficient fuel burn results in maximum power and fuel economy.

In addition to higher octane levels, premium fuels usually have additives and detergents that also:

  • Reduce carbon buildup around engine components that increases friction and reduces fuel efficiency
  • Prevent corrosion

By keeping your engine cleaner, these additives may help extend the longevity of engine components and reduce maintenance costs.

What Premium Gas May Do for Your Car

Ounce per ounce, premium and regular gasoline have the same energy potential. In other words, premium gas itself will not give you more power or more mpgs. However, because it facilitates a cleaner, hotter fuel burn, you are more likely to realize your engine’s full power potential.

Premium fuel is also likely to burn cleaner, resulting in less emission (i.e. better emissions test results).

Definitely Choose Premium Gas If…

Any vehicle that runs on unleaded fuel can run on regular or premium gasoline. However, there are some vehicles for which it is important to choose premium gas, including:

  • Vehicles whose manufacturers require premium fuel

You will have to check your owner’s manual to see if your vehicle manufacturer requires or recommends premium fuel. Although there is some debate, using regular gas in a vehicle with premium fuel requirements could void your warranty. It could also result in engine knocking—that’s what happens when gas ignites too soon—and that can lead to expensive engine damage.

  • Cars with turbocharged engines

The boost in air pressure resulting from turbochargers can also increase heat in the engine. So, even if your vehicle does not have a high-compression engine, the turbocharger creates similar conditions, making premium fuel important for knocking prevention.

  • Older, heavier cars

Older vehicles do not have computerized engine diagnostics that can automatically adjust spark plug timing to ensure fuel ignition at the right time. So, it is important to ensure they have fuel that will prevent pre-ignition (knocking) that can cause severe engine damage.

If your vehicle manufacturer only recommends premium fuel, then you can choose any grade you want. However, you may want to fill up with premium on occasion to compare performance and let the detergent additives help clean out the system.