Is it okay to use cheap regular gasoline in your car?

Is it okay to use cheap regular gasoline in your car?

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The national average for a gallon of gas hit a record high of $4.17 Tuesday, but it’s much worse than that for some motorists.

The national average price for a gallon of gasoline reached $4.17 on March 8, but is higher in several states, including Washington.
(Bill Clark/CQ-Roll Call, Inc via Getty Images)

This relatively low price is for regular fuel, while the mid-tier is $4.46 and the premium is $4.74. Historical costs have a lot drivers wonder if they can make do with the cheap stuff.

Some vehicles, especially high performance models, recommend or even require high octane fuels, while others only promise their best power and efficiency if you use them.

For example, Ford recommends using premium 91-octane gasoline in the Ford Mustang GT to get the most out of its 460-hp V8, but it can run on regular 87 octane without any issues. Meanwhile, the 760-hp supercharged V8 in the Mustang Shelby GT500 requires at least 91 octane, but the owner’s manual says 93 octane is preferable, especially if you’re going to be enthusiastically driving it on a track.

Vehicles have different octane requirements depending on the type of engine they use.

Vehicles have different octane requirements depending on the type of engine they use.
(David Ryder/Bloomberg via Getty Images)

Dr. Benjamin Lawler, Associate Professor at Clemson University International Automotive Research Centerexplains that high-performance engines that run at higher compression ratios or use forced induction — turbochargers and superchargers — are more susceptible to a condition known as knock.

Knocking occurs when fuel injected into a cylinder automatically ignites out of phase with the flame front ignited by the spark plug, creating pressure waves that can damage engine parts. Higher octane fuels are harder to ignite and resist this effect.

“It’s really just the rate of energy release, the rate at which energy is released,” Lawler said. “Another way to think about it is that the amount of time the energy is released is too small.”

Modern cars have electronic knock sensors that monitor what’s happening in the cylinder and can adjust their calibration based on the fuel being used, but some engines have a narrower operating window.

89 octane gasoline like Exxon's Plus is among the least popular types.

89 octane gasoline like Exxon’s Plus is among the least popular types.
(Bill Clark/CQ-Roll Call, Inc via Getty Images)

Lawler said drivers should follow what the owner’s manual says about fuel requirements, especially for vehicles over 20 years old, but newer ones can probably handle a tank or two of quality fuel. sub-optimal quality at a glance. It would probably take a few hundred miles of knocking driving before significant damage was done, and you should top up the gas as soon as you hear it. There are also warranty issues related to using the wrong fuel to consider, and the SAE (Society of Automotive Engineers) agrees it’s best left to the manufacturer.


A curveball is an 89 octane fuel, which is not generally used as a benchmark by car manufacturers and has little practical reason to exist. Consumers have apparently understood this, as it accounts for less than 10% of gasoline sold, compared to around 80% for regular gasoline.

It is essentially a mixture of 87 octane and 91 octane gas in the pump, and its main advantage over ordinary is that it benefits from the higher concentration of detergent additives contained in premium fuel. These can help keep fuel systems clean, but are not essential to the operation of a new car. Still, Lawler said refueling with a mid- or premium-grade tank is worth it once in a while for that reason alone.

“It’s probably a good idea to do this about once a year, just to keep your engine running smoothly,” Lawler advised.