5 Ways to Tell if Your Gasoline Has Gone Bad

Fuel can degrade and become unusable in as little as four weeks.

Ronan Glon | 

May 23, 2024 | 3 min read

Austin Lott | Capital One

Like milk and meat, gasoline has an expiration date. It can go bad in a few months when it's in your car's fuel tank, or it can last for about six months when stored in the right conditions. While old gasoline normally can still burn, it can cause your engine to run poorly. Here's how to tell if it is past its shelf life.

It Has a Strange Smell or a Strange Color

While most people wouldn't call the smell of gasoline pleasant, old gasoline smells particularly unpleasant. You shouldn't have to stick your nose directly into a jerry can or your car's fuel filler to get a whiff of it; you should be able to smell it as soon as you take off the cap.

Some describe the smell as sour. If gasoline smells like something other than gasoline, there's a chance it has become too old to use. Gasoline fumes can cause headaches, nausea, and dizziness, so don't spend a lot of time sniffing to check for freshness.

Gasoline loses its yellowish color and becomes darker as it expires. If you're worried about the gasoline in your car, you might be able to see its color through the inline fuel filter found in the engine bay, though most modern cars don't have one.

If you're worried about gasoline that's in a can, you can pour a little bit of it into a clear container to check its color. Never siphon fuel with your mouth, though, as swallowing even a small amount of it can make you sick. If you need to get fuel out of a tank, use a pump instead. Remember to siphon into a container designed to hold gasoline and dispose of it properly once drained.

There Is Debris in the Fuel Filter

As gasoline ages, its chemical composition changes and a gum-like substance begins to form in it. The fuel filter's role is to trap particles before they reach the engine, so a dirty filter full of debris can indicate you're burning old gasoline. The filter may not be easily accessible, however. Replacement of a fuel filter is often best left to a professional.

Your Car Is Running Poorly

Listening to your car is another way to tell if gasoline is too old. While you won't see a "fuel too old" error message in the instrument cluster, bad gasoline can trigger a "check engine" light, cause your fuel consumption to increase, and make your car more difficult to start.

Burning old gasoline can also cause a rough idle and sluggish acceleration, though these problems could be linked to other, non-fuel-related issues. Over time, old gasoline can begin to corrode parts of the fuel system, which may eventually lead to a poorly running engine.

It Has Been Sitting for a Long Time

Gasoline can become unusable in a matter of months, so if in doubt, assume that it's too old to use. If you park your car for six or more months — to store it in winter, for example — without putting fuel stabilizer in the tank, it's recommended that you drain the tank before trying to start the engine. The process of draining a fuel tank varies from car to car.

When in doubt about the age of the gas in your tank, it's often wise to err on the side of caution and have your car towed to a repair shop to have the tank drained.

Ronan Glon

Ronan Glon is an American journalist and automotive historian based in France. He enjoys working on old cars and spending time outdoors seeking out his next project car.