How Long Can You Leave Gas in a Generator? Updated Guide 2024

Generators have become indispensable in modern lives, providing essential power backup during emergencies and a reliable energy source in remote areas. However, to ensure their optimal performance and longevity, it is crucial to understand how long can you leave gas in a generator.

How long can you leave gas in a generator?

Proper gasoline storage in your generator is crucial to ensure its reliable performance when you need it most. The shelf life of gasoline can be affected by various factors, and it’s essential to know how long can you leave gas in a generator.

Short-term storage guidelines (1-3 months)

If you plan to use your generator frequently or in the near future, short-term storage is the way to go. In this case, you can store gasoline in your generator for up to three months without significant issues. However, it’s vital to use a fuel stabilizer to keep the gasoline fresh and prevent degradation. 

Additionally, store the generator in a cool, dry place away from direct sunlight and temperature fluctuations. Remember to check the manufacturer’s guidelines for specific fuel usage and storage recommendations.

Long-term storage recommendations (3+ months)

Special considerations come into play for extended periods of non-use, such as during seasonal changes or infrequent generator usage. Gasoline tends to degrade over time, leading to engine problems and affecting your generator’s performance. If you anticipate not using the generator for three months or more, it’s best to drain the gasoline from the fuel tank and the carburetor.

To prepare for long-term storage, run the generator until the fuel system is empty, preventing any remaining gasoline from causing damage. Once drained, ensure all gasoline residues are cleared from the tank and carburetor to avoid clogging and varnish buildup. Remember that gasoline may degrade in storage containers during long-term storage, so consider using the old gasoline in your vehicle or other equipment, and replenish your generator with fresh fuel when needed.

Signs that gasoline may no longer be suitable for use

Gasoline stored for an extended period can go bad, making it unsuitable for use in your generator. It’s important to recognize signs of degraded gasoline to avoid potential damage to your generator’s engine. 

Common indicators of bad gasoline include a foul smell, the presence of sediments or cloudiness in the fuel, difficulty in starting the generator or erratic performance. If you notice any of these signs, it’s best to drain the old gasoline and replace it with fresh fuel before using the generator.

What are the Effects of Storing Gasoline in a Generator?

Understanding the effects of storing gasoline in your generator is crucial for ensuring its optimal performance and longevity. Gasoline can undergo degradation over time, leading to several potential issues impacting your generator’s functionality.

How Long Can You Leave Gas in a Generator

1-Fuel degradation and its consequences

Gasoline is a volatile fuel that can degrade due to exposure to air, moisture, and temperature fluctuations. As gasoline breaks down, its chemical composition changes, forming gums, varnishes, and other deposits. 

These deposits can clog the fuel system, including the carburetor and fuel lines, reducing fuel flow and impairing engine performance. Additionally, degraded fuel may not burn efficiently, causing decreased power output and potential damage to the generator’s engine.

2-Potential damage to the generator’s components

Storing gasoline for extended periods without proper precautions can harm the generator’s vital components. Varnish and gum deposits from fuel degradation can coat internal engine parts, causing increased friction and wear. 

This can lead to overheating, reduced engine efficiency, and even permanent damage to critical components. Over time, the build-up of these deposits may necessitate costly repairs or even the replacement of engine parts, impacting your wallet and the generator’s overall reliability.

3-Impact on generator performance and fuel efficiency

The quality of the stored gasoline significantly affects your generator’s performance and fuel efficiency. Fresh, high-quality gasoline ignites more effectively and provides consistent power output. On the contrary, degraded gasoline may lead to engine misfires, sputtering, and decreased fuel efficiency, reducing the generator’s runtime and overall capacity to supply electricity. 

To ensure your generator functions optimally during power outages or emergencies, it is essential to maintain the quality of the gasoline it runs on.

Best Practices for Storing Gas in a Generator

Proper gasoline storage in your generator is essential to maintain its efficiency and performance. Following these best practices ensures that the fuel remains fresh and your generator is always ready to provide reliable power.

Using fuel stabilizers to prolong shelf life

Fuel stabilizers are additives designed to prevent gasoline from degrading over time. Adding a fuel stabilizer to the gasoline in your generator before storage can help inhibit the formation of varnishes and gums, keeping the fuel stable and suitable for use even after extended periods of non-use. Be sure to follow the manufacturer’s instructions when using fuel stabilizers, as overdosing can adversely affect the fuel’s quality.

Choosing the right storage container

Selecting the appropriate storage container is vital to maintain gasoline quality. Use containers specifically designed for fuel storage, preferably made of metal or approved plastic materials resistant to corrosion and leaks. 

Ensure the containers have a tight-fitting cap or lid to minimize exposure to air and moisture, which can contribute to fuel degradation.

Storing the generator in a suitable location

Where you store your generator can also impact the gasoline’s shelf life. Choose a well-ventilated, cool, and dry location to prevent temperature fluctuations and minimize exposure to sunlight, which can accelerate fuel breakdown. To ensure safety, avoid storing the generator in areas with excessive humidity or near potential ignition sources.

How to Properly Drain Gas from a Generator?

After knowing how long you can leave gas in a generator, properly draining gas is essential for its maintenance and to prevent fuel-related issues. Regularly removing old gasoline can help maintain the generator’s performance and prevent potential damage to its engine.

How Long Can You Leave Gas in a Generator

Safety first

Before starting, ensure the generator is turned off, and it has cooled down sufficiently. Working with fuel can be hazardous, so use safety gloves and eye protection.

Locate the fuel shut-off valve

Find the fuel shut-off valve on the fuel line or the fuel tank. Turn the valve to the “Off” position to stop the fuel flow.

Prepare a container

Place a suitable container beneath the fuel tank to catch the old gasoline as it drains. Make sure the container in which you catch the old gasoline is clear.

Remove the fuel cap

Open the fuel cap to allow air to enter the tank, facilitating a smooth flow of gasoline during draining.

Drain the gasoline

Depending on your generator model, you may need a siphoning tool or a fuel line to extract the old gasoline from the tank. Gently tilt the generator if necessary to ensure all the fuel is drained.

How Long Can You Leave Gas in a Generator

Dispose of the old gasoline properly

Gasoline is hazardous waste and should be disposed of responsibly. Take it to a designated collection site or contact your local waste management facility for guidance on proper disposal.

Safe disposal or reuse options for old fuel

Disposing of old gasoline responsibly is essential for both environmental and safety reasons. Never pour gasoline down drains, into the soil, or burn it. Instead, consider reusing the old gasoline in your vehicle or other equipment that can handle aged fuel. 

Mixing it with fresh gasoline can also dilute any potential issues with the older fuel. If reusing is not an option, contact your local waste management authorities to learn about safe disposal methods.


Is it okay to leave gas in the generator?

If you have a question about how long can you leave gas in a generator, then this short guideline is for you. It’s generally not recommended to leave gas in a generator for an extended period. Storing fuel for too long can lead to fuel degradation, causing starting issues and potential damage to the generator’s engine. 

To keep your generator in good condition, try to use fresh fuel, and if you anticipate not using the generator for more than a month, consider using a fuel stabilizer or draining the remaining gas.

What do I do if I left the gas in my generator?

If you left gas in your generator, don’t worry! Here’s what you can do: First, turn off the generator and let it cool down. Then, carefully drain the old gas from the tank into an approved container. Dispose of the old gas properly at a recycling center or an authorized disposal facility. 

Next, refill the tank with fresh, clean gasoline. Remember to check your generator’s manual for specific instructions on fueling and maintenance.

How often should I change the gas in my generator?

To ensure your generator’s optimal performance and longevity, it is recommended to change the gas after each use. Generally, it is best to refresh the fuel every 30 days if your generator is not in constant use. 

Stale gasoline can lead to fuel system clogs and hinder smooth operation. Additionally, consider using a fuel stabilizer to preserve the gas quality during long periods of inactivity.


Many busy people who have generator sometimes don’t have time to change the gas, and they ask how long can you leave gas in a generator. For a short duration, 1-3 months, and for a long term, 3 months plus, but living gas for a long time in a generator also affect its performance. It’s best to change the gas of the generator after each use. Regularly changing the generator’s gas will help you with a backup plan and achieving aspect results.

Engr. Amna has been working with on multimeterworld from 2019 and have worked on multiple projects as team leader. He is currently working in JDW Sugar mills and love to write electrical testing guides. His aim is to help 1 million people each year.