How Long Can Gas Sit In A Lawn Mower Without Going Bad?

Gasoline is an important component of a lawn mower, enabling it to run smoothly and efficiently. But when storing gas, it’s important to consider how long it can last without going bad. This is an important question to consider, as old gas can cause damage to the machine and reduce its effectiveness.

In this article, we’ll look at how long gas can sit in a lawn mower without going bad.

How Long Can Gas Sit In A Lawn Mower?

You’ve come to the right place if you have a lawn mower and have been wondering how long gas can sit in it without going bad. Gas can last for a certain amount of time before it starts to deteriorate, but it’s important to understand the factors that contribute to it going bad in the first place. The primary factor is the type of gas you’re using and the exposure to air and sunlight. The most important factor is when the gas sits in your lawn mower.

Gas is a mixture of petroleum-based hydrocarbons and additives, which can start to break down over time. If unleaded gasoline is used, it will break down after about three months if left in your lawn mower.

If you’re using ethanol-blended gasoline, it will last for up to six months. However, if you’re using an older lawn mower, likely, the gas won’t last as long as it would in a newer one, so it’s important to consider that.

In addition to the type of gas and the age of the lawn mower, another factor that affects how long gas can sit in a lawn mower is the exposure to elements such as air and sunlight.

Exposure to air can cause the gasoline to evaporate and become less effective, while exposure to sunlight can cause it to break down. If your lawn mower is stored in a garage or shed, it likely won’t be exposed to these elements, so the gas should last longer.

The best way to ensure that gas doesn’t go bad in your lawn mower is to make sure that you use it regularly. If you’re only using your lawn mower every few weeks or months, it’s important to make sure that you empty the gas tank and fill it with fresh gas. This will ensure the gas doesn’t have a chance to break down and go bad.

How To Store Gas For A Lawn Mower

How To Store Gas For A Lawn Mower?

Gasoline can last up to three months in a lawn mower without going bad if stored properly. Gasoline starts to degrade soon after being pumped from a fuel station and can become unusable if not treated with the proper additives. To help extend the life of gasoline in a lawn mower, it is important to use a gas stabilizer additive designed to help prevent the gasoline from going bad.

Gas stabilizer additives contain a variety of components that help to protect gasoline from the elements, such as oxygen, water, and heat. These components help slow the oxidation process that causes gasoline to break down and become unusable. The stabilizer also helps to reduce the formation of deposits and gum that can cause various problems in a lawn mower engine, such as fuel system clogs and misfires.

When adding a stabilizer to the fuel, it is important to follow the directions on the label carefully. Generally, this will involve pouring the stabilizer into the fuel tank and then running the lawn mower for a few minutes to ensure that the stabilizer is mixed thoroughly.

If the fuel is left sitting for more than three months, it is recommended to replace the fuel with fresh gasoline, as the stabilizer may not be able to protect the gasoline from going bad.

Benefits Of Adding Fuel Stabilizers To Gasoline

Adding fuel stabilizers to gasoline can have several benefits.

  • Longevity: Fuel stabilizers are designed to prevent gasoline from deteriorating over time. They can help extend the fuel’s shelf life, which is especially useful for those who use small engines infrequently, such as lawn mowers or generators. This can save you money by reducing the need to replace stale gasoline constantly.
  • Improved Performance: Stabilizers can also help improve gasoline performance. They can prevent the formation of gum and varnish deposits that can clog fuel lines, carburetors, and injectors. The stabilizer can help maintain the proper air-fuel mixture and prevent engine problems by keeping the fuel system clean.
  • Easy Start-ups: When gasoline sits for a long time, especially in equipment with small engines, it can become harder to start. Fuel stabilizers can prevent the fuel from breaking down and evaporating, ensuring easier startup even after long inactivity.
  • Protects Against Ethanol Damage: Many fuel stabilizers also have additives that protect against the harmful effects of ethanol in gasoline. Ethanol-blended fuels can cause corrosion and deterioration of fuel system components. A fuel stabilizer with ethanol treatment can help prevent these issues and prolong the life of your engine.
  • Cost-effective: Using fuel stabilizers can be more cost-effective than constantly replacing stale gasoline or dealing with engine problems caused by fuel degradation. It’s a small investment that can save you money in the long run.

Symptoms Of Bad Fuel In A Lawn Mower

Some common symptoms of bad fuel in a lawn mower include:

  1. Difficulty starting: If your lawn mower is having trouble starting or constantly stalling, it could be a sign of bad fuel. Old or contaminated fuel can clog the carburetor or fuel lines, making it difficult for the engine to start and run smoothly.
  2. Rough running: Bad fuel can cause the engine to run roughly or sputter. This may result in uneven cutting or decreased power output from the mower.
  3. Black smoke or exhaust fumes: If you notice excessive black smoke or strong-smelling exhaust fumes coming from the mower, it could indicate the presence of bad fuel. This is often caused by a rich fuel mixture or contaminants in the fuel.
  4. Fuel leaks: Another symptom of bad fuel is the presence of fuel leaks in the mower. Contaminated fuel can cause seals and gaskets to deteriorate, leading to fuel leaks around the carburetor or fuel tank.
  5. Poor performance: Lawn mowers running on bad fuel may experience decreased performance, including reduced cutting efficiency and overall power output. This can result in an uneven or patchy lawn.

Advances In Ethanol-Free Gasoline

Advances In Ethanol-Free Gasoline

If you’ve ever tried to start a lawn mower with old gas, you know how frustrating it can be. You might wonder how long gas can sit in a lawn mower without going bad. The answer to this question depends on a few factors, such as the type of gas used, the storage conditions, and the age of the gas.

Gasoline is a volatile fuel, meaning it can degrade over time. If stored improperly, the gasoline in your lawn mower can go bad in as little as 30 days. Exposure to oxygen, sunlight, and extreme temperatures can all cause gasoline to break down.

Storing your gas in a cool, dry place, away from direct sunlight and oxygen, is important to prevent this. You should also consider using gas stabilizers, which can help prolong the life of the gasoline.

The age of the gas also matters. Gasoline typically has a shelf life of about 3 months, so if you’re using gasoline older than this, it’s best to discard it and get fresh fuel. Also, certain fuel types, such as ethanol-blended gas, can degrade more quickly, so checking the expiration date before adding it to your lawn mower is important.

Finally, keeping your lawn mower’s fuel tank full is important. This helps to prevent air from entering the tank, which can cause the gasoline to deteriorate more quickly. Additionally, it’s best to use gasoline specifically designed for lawn mowers, as this fuel is designed to burn cleanly and efficiently.

The Impact Of Temperature On Stored Gasoline

When performing maintenance, the question of how long gas can sit in a lawn mower without going bad is important. This is especially true for those living in areas with cold climates because the temperature can significantly impact stored gasoline.

Cold temperatures cause the fuel to become more viscous, which reduces the combustibility of the gasoline and can even render it unusable. If gasoline is stored in a lawn mower for too long, the fuel may separate and form a sludge that can clog the mower’s carburetor and cause it to run incorrectly.

Because of this, it is important to know the proper storage methods for gasoline and the average lifespan of fuel stored in a lawn mower. Generally, gasoline should be stored in a cool, dry place with the lid securely on the container.

Gasoline should also be stored away from heat sources or ignition, such as furnaces or water heaters, because these can cause the fuel to vaporize and become dangerous. When stored properly, gasoline can last up to two years without going bad.

However, if the gasoline is stored in a lawn mower, it may only last for a while. Due to the vibration of the engine and the heat generated by the running of the mower, the fuel’s lifespan can be drastically reduced. The fuel can start to break down in as little as three months, so it is important to check the gasoline in your lawn mower regularly and replace it if necessary.

It is also important to consider the temperature when storing gasoline. In cold climates, the gasoline should not be stored in the mower for more than one month because the cold temperatures can cause the fuel to become more viscous and reduce its combustibility. In warmer climates, the fuel can last up to two months if stored properly.

The Pros And Cons Of Using Ethanol In Gasoline

There are both pros and cons to using ethanol in gasoline. Here are some of the main points to consider:


  • Renewable Energy: Ethanol is made from plant materials, such as corn or sugarcane, which are renewable resources. Using ethanol as a fuel additive reduces dependence on fossil fuels and helps to decrease greenhouse gas emissions.
  • Domestic Production: Many countries, including the United States, produce ethanol domestically. This reduces reliance on foreign oil and strengthens the country’s energy independence.
  • Economic Benefits: The production and use of ethanol can have positive economic impacts. It creates jobs in the agriculture and biofuel industries, and it can provide new market opportunities for farmers.


  • Lower Energy Content: Ethanol contains less energy per volume than gasoline. This means vehicles running on ethanol-blended fuel may experience slightly reduced power and fuel efficiency.
  • Compatibility: Not all engines and vehicles are compatible with high ethanol blends. Ethanol can damage certain rubber and plastic components in older vehicles. So, it is important to check the compatibility of your vehicle before using ethanol-blended gasoline.
  • Increased Food Prices: Ethanol production requires many crops, such as corn. This can lead to higher demand for these crops, increasing food prices and potentially impacting food security in certain regions.

Tips For Safely Handling And Storing Gasoline

Tips For Safely Handling And Storing Gasoline

When it comes to safely handling and storing gasoline, there are a few tips you should follow.

  • Always handle gasoline outdoors or in a well-ventilated area. Gasoline vapors can be highly flammable, so avoiding any potential ignition sources like open flames or sparks is important.
  • Use approved containers for storing gasoline. Ensure the container is specifically designed for gasoline storage and in good condition, with no leaks or cracks. It should also have a tight-fitting cap.
  • Keep gasoline containers tightly sealed and in a cool, dry place. Avoid storing gasoline in direct sunlight or areas with high temperatures, as this can increase the risk of vapor pressure build-up or even ignite the gasoline.
  • Store gasoline away from living spaces and ignition sources. It should be kept in a well-ventilated shed or detached garage, away from any potential sources of heat or flames.
  • Label containers. Always mark the containers with the word “gasoline” and avoid using makeshift labels that can be easily removed or mistaken for other substances.
  • Avoid overfilling containers. Gasoline expands when it gets warmer, so leaving some room for expansion when filling containers is important. Overfilled containers can leak or burst, leading to potential accidents.
  • Keep gasoline away from children and pets. Make sure to store gasoline in a secure location where it is not accessible to curious hands or paws.
  • Use caution when refueling vehicles or equipment. Avoid spills by using a funnel or nozzle to pour gasoline. Clean up any spills immediately and dispose of any rags or materials used to clean up safely.

The Importance Of Properly Maintaining A Lawn Mower

For homeowners responsible for the upkeep their lawn mowers, it is important to understand the importance of properly maintaining the machine. This includes knowing how long gas can sit in a lawn mower without going bad.

The lawn mower’s gas tank is essential for running the machine properly. If the gas is left too long in the tank, it can become stale and degrade. This can lead to various problems, including engine failure and other costly repairs.

The first step in understanding how long gas can sit in a lawn mower is how fuel works. Gasoline is a volatile substance that can quickly break down when exposed to air, light, and heat. With proper maintenance, the fuel in the tank can break down over time and become usable. For this reason, it is important to check the gas in the tank regularly and ensure it has stayed active.

In addition to regularly checking the fuel, using the correct fuel type for the machine is important. Different fuel types have different shelf lives, so it is important to read the manufacturer’s instructions to ensure you are using the correct fuel type for your machine. It is also important to ensure the fuel is stored in a cool, dry place away from direct sunlight.

It is also important to understand that the time that gasoline can sit in a lawn mower without going bad will depend on the quality of the fuel. Lower-quality fuel may go bad faster, while higher-quality fuel may last longer. In general, it is recommended that you replace the fuel in the tank every two months to ensure it is still in good condition.

Finally, it is important to remember that the fuel in the tank should be drained and replaced completely if the machine is not being used for an extended period of time. This can help extend the fuel’s life and prevent it from worsening. By following these steps and understanding the importance of properly maintaining the fuel in a lawn mower, you can ensure that your machine is running smoothly and that your fuel is fresh.

Common Causes Of Gasoline Contamination In A Lawn Mower

There are several common causes of gasoline contamination in a lawn mower. Here are a few possible reasons:

  • Stale or old fuel: If the gasoline in the lawn mower has been sitting for a long time, it can become contaminated and cause issues. Using fresh gasoline is recommended, and not keeping it for extended periods.
  • Water or moisture: Water entering the fuel tank can mix with gasoline and cause contamination. This can happen if the mower is left outside in the rain or the fuel cap is not properly sealed.
  • Dirty or clogged fuel filter: Over time, the fuel filter in a lawn mower can become dirty or clogged, leading to fuel contamination. Regular maintenance and cleaning of the fuel filter can help prevent this issue.
  • Improper storage: If the lawn mower is stored in a location with high humidity or extreme temperatures, it can contaminate gasoline. It is important to store the lawn mower in a dry and cool environment to avoid any potential issues.
  • Using low-quality gasoline: Using low-quality or cheap gasoline can increase the chances of contamination. It is advisable to use high-quality gasoline recommended by the manufacturer for optimal performance and to minimize the risk of contamination.

Should I Run My Lawn Mower Out Of Gas For Winter?

If you’re a lawn mower owner, you may wonder how long gas can sit in a lawn mower without going bad. This is an important question to consider, especially for those debating whether to run their lawn mower out of gas for the winter season.

Although running your lawn mower out of gas can help avoid the risk of an engine fire, it’s important to know that doing so can also cause damage to your machine and could cost you more money in the long run.

The truth is that gas can go bad in as little as 30 days. The more time passes, the more likely the gas will become contaminated with water and break down. This happens because water molecules are heavier than gasoline molecules, and they will sink to the bottom of the tank. This can lead to corrosion and rust in the tank, resulting in a poor fuel mixture that could damage the engine.

A fuel stabilizer is the best way to prevent your gas from worsening. These products are designed to keep gas fresh for up to two years and can be added directly to the fuel tank. This will help protect the engine from any buildup of corrosion or rust and will also help to keep the fuel mixture consistent.

If you’re concerned about leaving gas in the tank for the winter, running the lawn mower is best until it’s completely out of fuel. This will help to ensure that all of the fuel has been used up and will minimize the risk of any damage to the engine. It’s also important to remember that leaving gas in the tank for more than 30 days will not cause any damage to the engine, so long as you use a fuel stabilizer.


In conclusion, gas can sit in a lawn mower for up to three months without going bad. However, it is important always to use fresh fuel for optimum performance and to prevent potential damage to the engine. Furthermore, it is important to take preventative measures such as storing the mower in a cool, dry area and using a fuel stabilizer to ensure the fuel remains fresh.

Frequently Asked Questions:

Can I use 1-year-old gas in my lawn mower?

Using gas that is more than one month old in a lawn mower is not recommended. Gasoline can break down over time, which can cause damage to the engine, fuel system, and other components. If you must use old gas, add a fuel stabilizer to prevent damage and help keep the fuel from breaking down.

Can I leave gas in my lawn mower?

It is generally not recommended to leave gasoline in a lawn mower. Gasoline can start to break down and form deposits in the tank and other components, leading to engine problems. Additionally, it increases the risk of a fire hazard if it is not stored properly. If you must store gasoline for your lawn mower, it is best to use a fuel stabilizer and store it in a cool, dry place away from any sources of heat or sparks.

How long can petrol sit in a lawn mower?

Petrol should not be left in a lawn mower for more than 30 days. After that period, emptying the tank and refilling it with fresh fuel is recommended.

Can you start a lawn mower with old gas?

No, starting a lawn mower with old gas is not recommended. Old gas can cause serious engine damage and even void the warranty. It is best to empty the old gas of the mower and fill it with fresh gasoline before starting.

What type of fuel should I use in my lawn mower?

It depends on the type of lawn mower you have. Many lawn mowers run on gasoline, but some newer models may be designed to run on other fuels such as ethanol, biodiesel, or propane. Check your lawn mower’s manual to determine the type of fuel it requires.

How often should I change the oil in my lawn mower?

It depends on what type of mower you have and how much you use it, but generally, changing the oil in your lawn mower every 50 hours of use or every season is recommended.

How do I know when it’s time to service my lawn mower?

It is generally recommended that you service your lawn mower every season or after every 50 hours of use, whichever comes first. You should also check your owner’s manual for any specific maintenance requirements for your lawn mower model. Inspect the spark plug, air filter, oil, and blades for signs of wear or damage and replace or repair as needed.

What maintenance should I perform to keep my lawn mower running smoothly?

To maintain a well-functioning lawn mower, it is important to regularly change the oil and air filter, sharpen the blade, check and replace spark plugs, clean the mower deck, and keep the fuel system clean. By doing these tasks, you can ensure that your mower runs smoothly and efficiently.