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What to Do with Old Gasoline in Your Lawn Mower?

Maintaining a lawn mower is crucial for its longevity and efficiency, but one often overlooked aspect is the management of old gasoline. Using stale gasoline in your lawn mower can lead to a host of issues, from poor engine performance to long-term damage. This comprehensive guide will cover everything you need to know about handling old gasoline, including why it goes bad, how to identify it, and the best methods for disposal and prevention.


Understanding Why Gasoline Goes Bad

Gasoline has a limited shelf life. Over time, it degrades and loses its combustibility, leading to problems when used in lawn mowers and other small engines. Here’s a closer look at why gasoline goes bad:


Chemical Degradation


Exposure to air causes gasoline to oxidize, forming gums and varnishes that can clog the fuel system. This process begins as soon as gasoline is exposed to oxygen and accelerates over time.



Gasoline is a mixture of various hydrocarbons, some of which evaporate more quickly than others. As these volatile components evaporate, the fuel’s composition changes, reducing its efficiency and effectiveness.

Moisture Contamination

Gasoline can absorb moisture from the air, leading to water contamination. This is especially problematic for ethanol-blended fuels, as ethanol attracts water. Water in the fuel can cause rust and corrosion in the fuel system and engine.

Identifying Old Gasoline

Before taking any action, it’s important to determine whether the gasoline in your lawn mower has indeed gone bad. Here are some signs to look for:

Visual Inspection

Color Changes

Fresh gasoline is usually clear or slightly amber. Over time, it can become darker and develop a sour smell. If your gasoline appears darker than usual or has a cloudy appearance, it’s likely degraded.

Sediment or Particles

Check for any sediment or particles at the bottom of the fuel container or tank. These particles can clog the fuel filter and carburetor, leading to engine problems.

Engine Performance

Difficulty Starting

Old gasoline can make it difficult to start your lawn mower. If your mower is hard to start or requires multiple attempts, the fuel might be the culprit.

Poor Performance

If your lawn mower runs roughly, stalls frequently, or lacks power, stale gasoline could be affecting its performance. These symptoms often indicate fuel system issues caused by degraded fuel.

Proper Disposal of Old Gasoline

Disposing of old gasoline safely and responsibly is crucial to protect the environment and comply with local regulations. Here are some steps to follow:

Check Local Regulations

Different regions have specific regulations for the disposal of hazardous materials like gasoline. Contact your local waste management facility or environmental protection agency to understand the guidelines in your area.

Use Hazardous Waste Disposal Services

Many communities have hazardous waste disposal programs that accept old gasoline. These services ensure that the gasoline is disposed of in an environmentally safe manner. Locate a nearby hazardous waste disposal site and take your old gasoline there.

Automotive Repair Shops

Some auto repair shops and service stations accept old gasoline for proper disposal. Call ahead to check if they provide this service and what the requirements are.

Recycling Centers

Certain recycling centers accept old gasoline and other automotive fluids. Check with local recycling facilities to see if they have programs for accepting and recycling old gasoline.

Reusing Old Gasoline

In some cases, old gasoline can be reused if it hasn’t degraded too much. Here are a few methods to consider:

Mixing with Fresh Gasoline

If the gasoline is only slightly old, you can mix it with fresh gasoline to dilute the degraded components. Use a ratio of one part old gasoline to five parts fresh gasoline to minimize potential issues.

Fuel Additives

Fuel additives can help rejuvenate old gasoline by breaking down gums and varnishes, and improving combustion. Look for fuel stabilizers and conditioners designed to restore degraded fuel.

Using in Less Sensitive Engines

If the old gasoline is not heavily degraded, it can be used in less sensitive engines like those in lawn equipment, snow blowers, or generators. These engines are often more tolerant of lower-quality fuel than modern automotive engines.

Preventing Gasoline from Going Bad

Preventative measures can help extend the shelf life of gasoline and keep your lawn mower running smoothly. Here are some tips:

Use Fuel Stabilizers

Adding a fuel stabilizer to your gasoline can significantly extend its shelf life. Fuel stabilizers prevent oxidation and moisture absorption, keeping the fuel fresh for longer periods. Follow the manufacturer’s instructions for proper usage.

Store Gasoline Properly

Proper storage is essential to maintain the quality of gasoline. Store gasoline in a tightly sealed, approved container in a cool, dry place. Avoid storing gasoline in direct sunlight or near heat sources.

Rotate Your Fuel Supply

To ensure that you’re always using fresh gasoline, practice fuel rotation. Use older gasoline first and replenish your supply regularly. This practice helps prevent gasoline from sitting for too long and going bad.

Drain the Fuel Tank

If you know your lawn mower will be unused for an extended period, drain the fuel tank and run the engine until it stops. This prevents gasoline from sitting in the tank and degrading over time.

Regular Maintenance

Regularly maintaining your lawn mower can help mitigate the effects of old gasoline. Clean the fuel system, replace fuel filters, and inspect the carburetor to ensure everything is in good working order.

Handling Old Gasoline in Your Lawn Mower

When dealing with old gasoline in your lawn mower, it’s important to take the right steps to avoid damage and ensure smooth operation. Here’s what to do:

Draining the Fuel Tank

Start by preparing a suitable container to collect the old gasoline. Use an approved gasoline container to prevent spills and ensure safe storage.

Locate the fuel shutoff valve, if your mower has one, and turn it off. Then, use a siphon pump to remove the gasoline from the tank, or tilt the mower to drain the fuel into the container. Be sure to capture all the old gasoline to prevent contamination of the new fuel.

Cleaning the Fuel System

Inspect the Fuel Lines

Check the fuel lines for any signs of wear, cracks, or clogs. Replace any damaged lines to ensure proper fuel flow.

Clean the Carburetor

The carburetor is often affected by old gasoline. Remove the carburetor and clean it thoroughly with carburetor cleaner. Pay special attention to the jets and float bowl to remove any deposits or varnish.

Replace the Fuel Filter

Replace the fuel filter to ensure any remaining particles or contaminants do not reach the engine. A clean fuel filter helps maintain optimal engine performance.

Refilling with Fresh Gasoline

Once the fuel system is clean, refill the tank with fresh gasoline. Consider adding a fuel stabilizer to the new gasoline to extend its shelf life. Start the engine and let it run for a few minutes to ensure the fresh fuel circulates through the system.

See Also: Is Diesel Fuel Less Refined than Gasoline?

Environmental Impact of Improper Gasoline Disposal

Improper disposal of gasoline can have severe environmental consequences. Understanding these impacts underscores the importance of responsible disposal:

Water Contamination

Gasoline is a major pollutant of water sources. When disposed of improperly, it can seep into groundwater, rivers, and lakes, contaminating drinking water supplies and harming aquatic life.

Soil Pollution

Gasoline can contaminate soil, making it toxic to plants and animals. It can also affect soil structure and fertility, leading to long-term environmental degradation.

Air Pollution

Burning old gasoline or disposing of it inappropriately can release harmful vapors and pollutants into the air. These emissions contribute to air pollution and can have adverse health effects on humans and wildlife.

Fire Hazard

Gasoline is highly flammable. Improper storage or disposal increases the risk of fires and explosions, posing a significant safety hazard to people and property.

Legal Consequences of Improper Disposal

Disposing of gasoline improperly can also have legal repercussions. Most jurisdictions have strict regulations governing the disposal of hazardous materials. Violating these regulations can result in fines, penalties, and legal action. It’s essential to follow local guidelines and dispose of old gasoline through appropriate channels.

Case Studies and Examples

To further illustrate the importance of proper gasoline management, here are a few real-life examples and case studies:

Case Study 1: Environmental Impact of Gasoline Spill

In a small town, improper disposal of gasoline led to a significant spill that contaminated the local water supply. The cleanup process was costly and time-consuming, and the community faced health risks due to the contaminated water. This case highlights the critical need for safe disposal practices.

Case Study 2: Lawn Mower Engine Damage

A homeowner used old gasoline in their lawn mower, resulting in severe engine damage. The cost of repairs exceeded the value of the mower, leading to a complete replacement. This example underscores the importance of using fresh gasoline to maintain engine health and avoid costly repairs.

Case Study 3: Legal Consequences of Improper Disposal

A business was fined heavily for disposing of gasoline improperly, violating environmental regulations. The legal and financial repercussions were severe, serving as a warning to other businesses about the importance of adhering to disposal guidelines.


Managing old gasoline in your lawn mower is an essential aspect of maintenance that should not be overlooked. Understanding why gasoline goes bad, how to identify it, and the proper methods for disposal and prevention can save you from engine damage, environmental harm, and legal issues. By following the guidelines outlined in this comprehensive guide, you can ensure that your lawn mower runs efficiently and that you handle old gasoline responsibly. Regular maintenance, proper storage, and adherence to local regulations are key to effective gasoline management, helping you maintain your lawn mower and protect the environment.

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