When pulling up to a gas station, the cheapest gas usually seems the most appealing. After all, regular unleaded is cost effective and works just the same as the more expensive stuff, right? Maybe not.
For most drivers out there, filling up their tanks with regular gas is all that is required for their car's engine to run smoothly. But for others, with luxury or higher performance cars, their vehicles may need premium gas to ensure peak performance and avoid engine damage.
Yoichi Hamada, a self-proclaimed car guru, says the different grades of gasoline refer to the amount of octane that is in the fuel. Most gas stations offer three octane grades: regular, 87 octane; midgrade, 89 octane; and premium, 91 or 93 octane.
Premium gas, which can cost 15-30 cents more a gallon than regular, is more expensive, Hamada says, because the process of putting more octane in the gas costs more. Also, some companies add different additives to combat against buildups and emissions.
The higher the octane the more it resists detonation, or knocking, in the engine.
"Detonation is the pre-ignition of the fuel and air on the compression stage in the engine," explains Hamada. "This detonation can damage the engine's inner parts causing failure in your engine."
Depending on the car manufacturer and the engine specifications, some cars require premium gas. Higher specifications or engines with more horsepower will more than likely need a higher octane gas to resist knock and failure in the engine.
"For example, an economical Honda Civic base model will only need to run on regular gas, as it is a car that emphasizes on fuel economy and not on performance," Hamada says. "On the other hand a higher performance Honda Civic SI will need the premium gas, as they are high performance models that focus on horsepower, speed and performance."
If your car is not receiving the type of gas it requires, the damage to the engine can range from minor to catastrophic, which would require expensive repairs. Using a lower octane gas used for an engine that requires a higher octane can result in detonation, or knock, in the engine. That may damage the internal components, lower performance and possibly lower gas mileage.
According to blog by the advisers at Truecar, if your car requires premium gas, in most cases it won't hurt your car, or void the warranty, to use regular gas. The reason some cars require using premium gas is that the vehicle has a high-compression engine. Unless you hear knocking in your engine, there is no harm to your car by not using premium. Most modern cars have knock sensors and computers that adjust settings and maximize performance for various fuel grades.
However, fuel economy could be slightly reduced when using a lower-octane fuel. The experts at Truecar advise that if you're leasing your car, you may want to be more cautious about using premium if required by the manufacturer, in the off chance that using regular does affect the engine.
And for those who are considering upgrading to premium though your car doesn't require it, a recent consumer report from the Federal Trade Commission: "In most cases, using a higher-octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner."