How Long Does Gas Last Before Going Bad?

How Long Does Gas Last Before Going Bad?

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For excellent performance, your engine needs fresh fuel in the tank.

Whether providing optimum spark or ideal fuel mileage, gasoline works better within a specific time frame.

And with today's high-tech engines often requiring premium fuel, fresh gas ensures yours runs at an optimum level. 

But sometimes, you may not drive as much, and the gasoline in your tank can sit for days, weeks, and months. And since fuel gradually deteriorates over time, it's essential to take steps to ensure its freshness so that your car runs its best.

How long is your gas good for? When should you use a fuel stabilizer?

Let's look at the subject of gasoline shelf life and some steps you can take to maintain the fuel in your tank.

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How long does gasoline last?

After you fill up your tank with gasoline, it gradually spoils over time. If it goes bad, it might cause a variety of mechanical issues. 

"The key thing to remember is that gasoline is a living chemical," says Greg Bannon, AAA director of automotive engineering and industry relations.

The usual time range for gasoline's usefulness is around three to six months. And because fuel goes through several manufacturing and transportation steps before you pump it into your gas tank, knowing its age could prove a challenge. 

Manufacturers produce gasoline at a refinery and then store it in tanks for days — or even weeks — before it arrives at a gas station. And since service stations vary in the amount of customer traffic they receive, gas may sit for extended periods at certain ones. Because of that, gasoline may be more than a month old before it reaches your tank. 

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Ways to keep gasoline fresh

To keep your car's gas in good condition, you have several methods to choose from. 

When you find yourself driving less and a tank of gas lasts longer than expected, topping it off can help retain freshness. A full gas tank leads to less air inside, lowering the risk of excessive condensation and fuel spoilage. 

Another way of taking care of a tank of fuel is by routinely driving your car, even if that means taking it on brief trips. Not only does this prevent fuel degradation, but you'll also need to fill up the tank more often. 

Oxygen inside a fuel tank causes evaporation, leading to gasoline losing some of its chemical attributes. You can combat this by keeping your tank full, which reduces the oxygen inside. 

If you don't plan to drive your vehicle for an extended period, adding a fuel stabilizer to your car's tank is a trusted way of increasing your gasoline's longevity. 

When using a fuel stabilizer, it's best to add it to a full tank of new gas. However, if you add a fuel stabilizer to old gasoline, it'll still help to slow the degradation process. 

Gas stabilizer comes in a small bottle, and you can find it at your local auto parts store. Popular brands of fuel stabilizers include Sta-Bil and Sea Foam. 

If you need to store gasoline, keeping it in three-, four-, or five-gallon gas cans with air-tight covers and in a cool area with low humidity and oxygen helps retain freshness.

How to recognize bad gasoline

As gasoline resides inside a fuel tank, its chemical composition fluctuates and its octane decreases. If you have a high-performance or turbocharged engine requiring 93 octane premium fuel, old gas may lose its efficiency. 

You probably know what your engine sounds like when it's running correctly. Perhaps it idles steadily at a low RPM and accelerates smoothly. But if your engine won't start, idles roughly, or has diminished acceleration, the cause may be old gas. These issues could result from damaged fuel injectors or a broken fuel pump. In this situation, seeking out a mechanic may be the best option. 

If you notice an illuminated check engine light when you start your car, it might be a symptom of spoiled gasoline. If you maintain your vehicle regularly and keep the oil topped off, old fuel may be the cause.

And similar to food going bad, you can discover bad gasoline by noting its smell or appearance. Old gas exhibits a darker color than new fuel, and it also has a foul odor. 

If you believe you have a tank of spoiled gasoline, it's essential to pump it out and refill it with fresh fuel. 

The reason is that not only does old gas lead to your engine running poorly, it can also cause problems with internal parts and deposit a gummy substance in the fuel lines. And if you usually fill up with gasoline that contains ethanol, should it spoil, it can draw in moisture that causes corrosion in the fuel tank and fuel system. 

Keeping fresh fuel in the gas tank is just one way of maintaining a vehicle in excellent condition. And when you're in the market for a used car or truck, you want something that's been well-maintained and stands the test of time. With Shift's best-in-industry service contracts, you know your new-to-you vehicle's good to go, mile after mile. With a Shift Vehicle Protection plan, not only are essential components covered, but you receive roadside assistance. Wherever you happen to be in the continental U.S., Alaska, Hawaii, or Canada, help is just a toll-free phone call away, 24 hours a day, seven days a week, 365 days a year.

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Author
Shift Editorial Team