Fuel Void: Understanding Car Warranty Implications

Using the wrong fuel in your car can damage the engine and void your warranty. For example, using regular gas in an engine that requires premium could cause severe engine knock or pinging (premature ignition of the fuel) that damages the pistons or other engine parts. Check the owner’s manual to find out what type of fuel your car requires.

Using regular gas in an engine that requires premium could void your warranty

If you use regular gas in an engine that requires premium, it could void your warranty. This is most likely to happen if using regular causes severe engine knock or pinging (premature ignition of the fuel, also known as detonation) that damages the pistons or other engine parts.

GM says about the subject in an owner’s manual for a vehicle that requires premium: “Use premium unleaded gasoline with a posted octane rating of 91 or higher. If the octane rating is less than 91, you could damage the engine and may void your vehicle warranty.”

Some manufacturers recommend premium gas but say that regular or mid-grade gas can be used instead. They usually warn that using lower-octane gas could reduce performance.

Bottom line: Check the owner’s manual. If the vehicle manufacturer says the engine requires premium, believe it. Don’t try to save a few cents per gallon by buying regular gasoline. Doing so could lead to much larger expenses in the future.

Severe engine knock or pinging may damage the pistons or other engine parts

Severe engine knock or pinging (premature ignition of the fuel, also known as detonation) can damage the pistons or other engine parts. When the fuel-air mixture ignites prematurely or unevenly, it results in a knocking or pinging sound. This abnormal combustion process can cause severe damage to the engine components over time. Engine pinging can occur from a number of different root causes. While it can sometimes be easy to spot, it’s important to confirm with your local auto mechanic to confirm your findings.

An engine’s cylinders are designed to ignite the fuel-air mixture at a precise moment, causing a controlled explosion that pushes the piston down, generating power. However, when the fuel-air mixture ignites prematurely or unevenly, it results in a knocking or pinging sound. When you notice your vehicle’s engine knocking (sometimes perceived as a pinging sound), take measures to address the problem immediately before your engine is damaged. Pinging, or knocking, is audible evidence of premature combustion happening in one or more cylinders. It’s a major problem with expensive consequences if you ignore it. A well-tuned engine depends on accurate timing to provide optimum power, efficiency, and wear.

The rotating crankshaft alternately drives the piston up through the cylinder and then is driven back by the force of the piston as it descends. Simplified, the descending piston draws fuel and air into the cylinder, and then the ascending piston compresses the fuel/air mixture to optimize the power released at the point of ignition. When the peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle, the shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive. Knocking should not be confused with pre-ignition—they are two separate events. However, pre-ignition can be followed by knocking. The phenomenon of detonation was described in November 1914 in a letter from Lodge Brothers (spark plug manufacturers, and sons of Sir Oliver Lodge) settling a discussion regarding the cause of "knocking" or "pinging" in motorcycles.

Yes, engine knock creates extreme pressure in the cylinder that can damage internal engine components like the pistons, bearings, connecting rods, or the cylinder wall. It also raises the temperature in the cylinder dramatically, which could lead to more instances of pre-ignition. Most modern vehicles come equipped with knock sensors, which signal the vehicle's computer to adjust the ignition timing and fuel mixture when knock is detected. Since knock sensors generally protect the engine in most cases, a failing knock sensor means your engine could be suffering from pre-ignition without you (or the computer) noticing. So, by the time you actually hear engine knocking or pinging, it may have a failing knock sensor, or the engine knock may be severe enough that your vehicle's computer can't correct it on its own.

Using the wrong gasoline may cause decreased fuel economy and engine performance

If the vehicle manufacturer says the engine requires premium, believe it. Don’t try to save a few cents per gallon by buying regular gasoline. Doing so could lead to much larger expenses in the future. If you have a high-performance vehicle or participate in motorsports, exploring higher-octane race fuels may unlock additional performance gains. Personal preferences and priorities play a role in fuel selection. If you prioritize fuel efficiency and environmental sustainability, ethanol-based fuels or biodiesel may be worth considering.

There is a pervasive myth that using a higher-octane fuel is better for your car’s performance. Hint – it’s not. Typically, although there are some variations among engines, putting a higher-octane gas into your car than it requires will neither help nor hurt your car’s performance. There are some engines that are not designed to burn higher-octane fuel and you may see a reduction in power and fuel economy. This mistake should not cause any major damage to your car – just be sure to pick the correct octane gasoline next time you fill up. Whether done by mistake or done to try to save on fuel costs – putting low octane fuel into an engine that requires a higher octane can cause problems that destroy your engine.

Putting gasoline in a diesel car is also a serious mistake. Diesel engines rely on diesel fuel's lubricating properties, which gasoline lacks. Without proper lubrication, parts of the engine may grind together and cause significant damage. The fuel system will need to be drained, damage to the fuel pump and injectors must be addressed, and potentially a complete engine rebuild or replacement may be necessary. Some manufacturers recommend premium gas but say that regular or mid-grade gas can be used instead. They usually warn that using lower-octane gas could reduce performance.

Check the owner’s manual to see if the manufacturer recommends premium

If you are using regular gas in an engine that requires premium, it could void your warranty. This is because using regular gas could cause severe engine knock or pinging (premature ignition of the fuel, also known as detonation), which damages the pistons or other engine parts.

If you are unsure whether your car requires premium gas, check the owner's manual. If the vehicle manufacturer says the engine requires premium, believe it. Don't try to save a few cents per gallon by buying regular gasoline as this could lead to much larger expenses in the future.

If your manual states that premium is recommended, but not required, you have options. Vehicles that recommend, but do not require you to use premium, are letting you have your cake and eat it too. These cars have engine computers that can adjust to run on both lower-octane and higher-octane fuels.

Incorrect levels of gasoline may cause your engines to run poorly, or even break down faster over time. Always either check your owner’s manual thoroughly or do some research online about your new car before you play eeney-meeny-miney-moe at the gas pump!

Don’t try to save money by buying regular gasoline

Check the owner’s manual and listen to your car if you are unsure about what type of fuel to use. If the manufacturer says the engine requires premium, don’t try to save a few cents per gallon by buying regular gasoline.

Using regular gas in an engine that requires premium could void your warranty. This is most likely to happen if using regular causes severe engine knock or pinging (premature ignition of the fuel, also known as detonation) that damages the pistons or other engine parts.

Some manufacturers recommend premium gas but say that regular or mid-octane gas can be used instead. They usually warn that using lower-octane gas could reduce performance.

If heavy knocking is heard when using gasoline rated at 91 octane or higher, the engine needs service.

Using the wrong gasoline may cause other problems, like decreased fuel economy and engine performance.

Frequently asked questions