You may be filling up your car with the wrong gas

Drivers commonly use the term "twenty, regular, cash" in New Jersey, the only state where motorists are not allowed by law to pump their own fuel.

Like many things we buy, gasoline prices are very unpredictable. In today's climate, twenty dollars will only get drivers so far in between their next trip to the gas station, depending on their vehicle's fuel efficiency.

Filling up your daily driver is a significant expense, but many people must bite the bullet, especially as return-to-office policies have returned, displacing remote work.

Those who run their cars on regular gas may seem better off than those running premium grade because regular gas prices are significantly lower.

However, a new report by the U.S. Department of Energy shows that many people use the wrong fuel in their cars, potentially exposing them to a great risk of engine trouble.

A gas pump at a Shell station in Miami, Florida.
Joe Raedle/Getty Images

According to a recent Fact of the Week by the U.S. DOE, more than half of all new light-duty vehicles sold in the United States, like cars and pickup trucks, come with a premium fuel recommendation.

The federal agency says the statistic surpassed the 50% mark in 2018, a considerable increase from just 6.5% percent of cars in 1985.

The department only began tracking cars that run on mid-grade fuel—the one priced between regular and premium—in 2011. However, the list of models with mid-grade recommendations remains low.

More Automotive:

Why do so many cars only take premium?

In the past, automakers used to make cars produce more power by installing bigger engines, such as V6s and V8s, under the hoods of their models.

While this provided a reliable way to make cars faster and more capable of certain jobs, like towing, and allowed the more widespread use of cheaper, lower-octane gasoline, automakers had to return to the drawing board once stricter emissions regulations restricted the use of bigger engines.

These days, "big motors" like V6s and V8s are replaced with turbocharged inline-4 cylinder motors and V6s with higher compressions that produce the same or even more power than the engines they replaced.

However, the catch is that these engines require higher octanes, such as those in premium fuel, to work their best.

What does gas octane mean?

In simple terms, octane numbers reflect the fuel's ability to prevent engine knock, a harsh sound made when fuel and air burn unevenly inside an engine.

Higher octane fuels help increase pressure in the cylinder, allowing engines to generate more energy from air and fuel without pre-detonating, reducing the risk of engine knock.

Aside from fuels like ethanol-based E85, Sonoco's Ultra 94, and ultra-high octane racing gas, most American gas stations offer three grades: 87 octane for regular, 89 for midgrade, and 91-93 for premium.

The higher the octane rating, the higher the fuel's ability to prevent engine knock, allowing high-compression turbocharged engines to run at peak performance.

Do I really need to use Premium in my car?

The best bet for concerned car buyers or owners is to do thorough research about their cars or the cars they are interested in.

Typically, manufacturers disclose what fuel is needed in a certain car in its owner's manual or website.

If you use lower-octane gas in a car requiring premium-grade gas, you could expose your vehicle to damage, causing engine knock. In some situations, the damage from engine knock can lead to very expensive service bills.

You may also find your gas mileage and acceleration suffer, especially in tough driving conditions, like while towing.

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