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How Long Does Gasoline Last? | A Fuel Storage Guide

Gasoline is a pivotal commodity in modern Western life. In many circumstances, it may be necessary to store gas for future use. Such instances include wanting to stock up in approved containers when prices are low, or to make sure you have enough fuel to get through a winter in a remote location. How far into the future, though, will the stored gasoline be an effective fuel source?

Gasoline can be stored for up to 6 months without significant loss to its combustibility. To extend the shelf life to a year, add a fuel stabilizer to the gasoline prior to storage. The fuel should be kept in a plastic or metallic sealed container, and all contact with moisture must be avoided.

Additionally, the stored vessels ideally will be excluded from any source of heat and substantial temperature changes. Gasoline sitting in your fuel tank will start to degrade after a month due to its exposure to air.

Gas may seem to last a lot longer than 6 months, and my personal experience proves that gas can sit around the garage for a couple of years and still fire up the lawn mower. However, it might be doing harm to the engine. Oxidation and an unwanted accumulation of water in the fuel can occur over time. Even though the engine is actually firing up, you might be shortening its life.

Now, let’s take a closer look at the details of the problem.

Gas Can on Ground

What Is The Lifespan Of Gasoline?

Despite gasoline being readily available at the local pump, there is always a concern that this finite commodity may be in short supply. Consequently, storing gas may become necessary to get through prolonged periods or when prices are low and you wish to stockpile. Knowing how to preserve your gasoline correctly will protect your investment.

Several factors are involved when considering how long gasoline lasts. These include:

  • The storage container
  • Temperature
  • Oxygen levels
  • Humidity
  • The type of fuel

Related Can You Freeze Gasoline? | What You Need To Know.

If stored in a well-sealed container and away from heat, the gasoline you buy from the pump will last between 3 to 6 months. Following this time period, the quality of the gas will have degraded to the point where it won’t have sufficient combustibility to be used in most vehicles.

For motors in lawnmowers and related items such as weed wackers, the fuel may not have enough combustibility following 3 months of storage. The shortened shelf life is due to the ignition system’s efficiency, which tends to be of lower quality in garden equipment compared to a vehicle.

There are two main factors that can alter this 3-6 month longevity time frame:

1. Adding a Fuel Stabilizer

A fuel stabilizer can keep gasoline viable for 1-3 years if used correctly. They are made from petroleum products and work by preventing the oxidation and chemical breakdown of the fuel. Primarily, it is a mix of antioxidants and lubricants. The stabilizer bonds with the gasoline to repel water, prevent evaporation and protect the fuel from becoming sticky. Often old, viscous fuel can ruin engines by leaving a residue that can quickly ruin a carburetor. Therefore, its best avoided.

You only need a little stabilizer, around a few ounces, for a full car tank. Too much, and you will dilute the fuel, possibly lowering the power you can extract from it. For optimal results, add the stabilizer to a near-empty tank or container, then fill it will gas. This allows the stabilizer to circulate evenly within the fuel. When using the stored fuel in a motorized machine, run it for 5-10 minutes to get the stabilized fuel into the engine for maximum protection.

Here is my favorite brand and one that I highly recommend, available on Amazon.

2. Ethanol Content

Due to the desire to find an alternative, renewable fuel source, ethanol has become a popular additive to most gasoline sold. Unfortunately, ethanol has a negative effect on the longevity of gas as it oxidizes far quicker.

Additionally, ethanol is hydrophilic, meaning it attracts water molecules. Once water is trapped into the gasoline, it separates into distinct layers of ethanol and gasoline. This makes the blend hard to combust. Generally, the higher the ethanol content, the shorter the lifespan. E10, a fuel made up of 90% gasoline and 10% ethanol, will last around 3 months.

Pure gasoline will also be affected by evaporation and oxidation but at a much slower rate. Unadulterated gas is also hydrophilic, meaning it repels water. These properties result in pure gasoline lasting at least 6 months if stored optimally.

Gasoline stored in your gas tank will only last around a month. Such a short time frame is due to the fact your gas tank is not airtight. Therefore, gasoline is exposed to plenty of oxygen, which can oxidize and thus degrade it. Think ahead and keep vehicles such as boats, mowers, or generators that are going into storage with near-empty tanks. That way, you won’t need to remove old fuel before using them.

How To Store Gasoline

The best way to store gasoline is to keep it in a sealed plastic container or a metal tank. The volume of the chosen vessel should not exceed the county’s Fire Marshall’s recommendation, which is usually a maximum of 5 gallons. It is also a regulation to label the containers to keep up with fire code.

Having a sealed container is essential as this eliminates excessive air and moisture from coming into contact with the gasoline. While pure gas repels water, it will still mix with the fuel and lower its combustibility. For the same reason, keeping the fuel in non-humid conditions is vital to achieving the maximum shelf life.

I recommend getting a no-spill plastic gas can. This is my favorite one, found on Amazon. Not only is it nicely sealed, but it is also much easier to pour into lawn equipment without spilling it everywhere.

Other than increasing the water content, humidity, along with elevated temperatures, can make gasoline highly volatile. For these reasons, it is best to keep your stored fuel in cool and dry environments that are not exposed to direct sunlight. It should also be a place that is well-ventilated and void of electrical equipment and any open flames. Ideally, it would also be in an area that is separate from the house. By following these guidelines, the risks of storing fuel will be minimized.

During storage, get in the habit of periodically stirring the gasoline. Such care is especially required when trying to get the most out of your fuel stabilizer. Frequent mixing will help the stabilizer circulate and protect the fuel better.

Related Is it Safe to Keep a Gas Can in Your Car? | What to Know.

How To Identify If Gasoline Has Gone Bad?

Eventually, no matter how well you store your gasoline, it will expire. The first indication that fuel has gone stale in your engine is to try starting the motor. Whether it’s a car, scooter, generator, or lawnmower, the idle will be rough when the motor turns. While in your vehicle, if it starts, you will also probably notice that it will frequently stall during acceleration. In some instances, bad gas can make the check engine light come on in your vehicle.

  • If the questionable gas is not inside a tank, you can visually inspect it to look for signs of degradation. When gasoline ages, it oxidizes, causing it to change to a darker color. Just like food, a foul smell is a clear indication that gasoline is past its best too.
  • When gasoline has gone stale, you can still use it if you mix it with fresh fuel. For a vehicle, fill your tank to the three-quarter level, then top it off with the old gasoline. For a generator or lawnmower, a one-to-one ratio should still turn the motor over.

Using old gasoline alone, however, is not advisable. Bad gas can hurt the internal components of your engine as a result of its lower combustibility. Additionally, old gasoline can leave gum residue inside your engine components that can cause blockages inside the engine. If the fuel contains ethanol, there are dangers of vapor being drawn into the fuel line, which can lead to corrosion. 

How Do You Dispose Of Expired Gasoline?

When you’ve stored gasoline long after its expiration date, and it cannot be used to supplement fresh gas, it needs to be disposed of. Despite its lower combustibility rating, expired gasoline is still highly flammable and must be disposed of responsibly.

Even if you have a small volume to discard, do not be tempted to pour it down a sink, into a sewer, or near a body of water – it will contaminate the local environment and harm vegetation, wildlife, and drinking water. Instead, reach out to city waste or the local fire department for instructions.

Typically, you will be required to drive your expired fuel to a specific disposal site and pour your gas into a larger container there. Make sure you transport the fuel in an approved sealed vessel to prevent putting yourself in danger.

Related How Long Gas Lasts (And How To Make It Last Longer).

Octane Rating and Types of Gasoline

Before storing gasoline, it is essential to know what you are storing. There is no sense in preserving the wrong type of fuel for the intended use.

When at the pump, you may notice that there are three conventional fuel grades to choose from. Like me, you may have wondered if there is a benefit to buying the more expensive category.

In the fuel industry, the combustibility of the fuel is measured by its octane rating. The word octane is derived from what the fuel is made of – octane groups, a family of hydrocarbons.

The octane rating, however, is not a function of the chemical structure of the fuel. Instead, it corresponds to the benchmark performance of the mixture of iso-octane, which has a rating of 100, and n-heptane, which has an octane rating of 0. Therefore, gasoline with an octane rating of 88 corresponds to the performance you would get if you made a fuel mix of 88% iso-octane with 12% n-heptane.

Common Fuel Ratings:

  • 86, 87, and 88
    Most cars run on ordinary 87-octane gasoline. You may find this to be slightly different in high-altitude states, such as Colorado, as fuel burns somewhat differently when the oxygen content is lower. This octane level is sufficient for most vehicles.
  • 90 and Above
    High-end cars will need a higher octane grade to prevent knocking. Knocking in a vehicle is caused by high heat and pressure. This combination makes the fuel and air mixture ignite before the spark plug initiates a spark to begin the combustion. Over time, this will ruin your engine. If your car manufacturer recommends using a higher-octane fuel, do so.
  • E85
    In the search for renewable energy sources, the US government massively subsided corn production to make ethanol. As a result of these policies and the lack of use, the abundance of ethanol in this country was vast. Alas, ethanol has far lower chemical energy than gasoline, so it is not powerful enough to run a vehicle. However, it was determined that gas could be supplemented with ethanol, up to 15 % of the content (85% gasoline, 15% ethanol mix), without car performance being affected. It is generally cheaper and cleaner than pure gas. However, you will get fewer miles to the gallon due to its reduced power rating. 

Does Diesel Last Longer Than Gasoline?

Diesel is more fuel-efficient than gasoline due to its higher chemical energy rating. Diesel engine design is conducive to large, heavy-duty engines. It is different from gasoline due to the way it is ignited. Gas is mixed with air and ignited via spark plugs.

Whereas diesel engines compress the air first, then the fuel is injected. Compressing the air heats it, so once the fuel is introduced, it ignites. Thus, no spark plug is required. Diesel fuel is more stable than gasoline and will last 6-12 months without significant degradation if you keep it sealed, cool, and dry.

Important: Do not add gasoline stabilizers to your diesel fuel to make it last longer – you will adversely affect its combustibility. Instead, use diesel rated stabilizers to prolong its life.

If you are concerned that your diesel fuel may be bad or going bad, you can actually test it. Products like this one from fleet fuel testing can help monitor diesel fuel stores.


Unadulterated gasoline that you buy from the pump will last up to 6 months if it is kept in a sealed container away from excess moisture and heat. You can add a fuel stabilizer to the gasoline before it is stored to elongate its life, enabling gas to have sufficient combustibility for 1-3 years.

For extended shelf lives, only store pure gas, not an ethanol-containing mixed blend. Ethanol is hydrophilic (water-attracting) and oxidizes (degrades) more quickly than gasoline. Consequently, ethanol blends only last around 3 months without a stabilizer and up to 6 months with it.

When storing gasoline, keep it in an approved plastic or metallic container, away from heat sources, including sunlight, preferably away from other flammable items like your home. Which gasoline you choose to store depends on which fuel grade (octane rating) your engine needs and how long you need it to last. 

Final Take

While researching this topic, some of the information we gathered from authorities on the subject seemed to be really conservative and often conflict with our real-world experience.

Case in point: Multiple times over the years, I have let gas sit around the garage for two to three years and had it still seem to work fine. So, what gives?

The way I look at it is that gas probably does indeed begin to degrade after about 6 months, depending on storage conditions. It begins to degrade. And while it may still work in that lawn mower or vehicle, it probably isn’t ideal and could even be shortening the life of the engines.

Unfortunately, it appears that there isn’t a test you can purchase for gasoline. However, here is an interesting video that shows that bad gas can definitely look a lot different than fresher gas.

Related Questions

What Are Alternative Fuel Sources For Cars?

Gasoline is a non-renewable energy that has affected our environment and assisted in climate change. Consequently, research has been ongoing for years on how to replace gas derived from fossil fuels.

Even so, despite this quest, most progress has been made with electric cars. Although electric vehicles release fewer emissions than gasoline motors, most of our electricity is still made by burning coal or natural gas, causing issues with the environmental argument. Ethanol has been added to most gasoline you buy at the pump, which helps reduce the amount of gas used.

However, making ethanol is an energy-intensive process and doesn’t help much with the overall problem. Presently, there isn’t an energy-efficient method for powering cars that could overtake gasoline.