Many homeowners have experienced the frustration of a lawn mower that refuses to start after sitting idle for a few months. While various factors can contribute to this issue, one of the most common culprits is often overlooked: old gasoline. The question, “Can old gas break a lawn mower?” is a valid concern, and the answer is a resounding yes. Let’s delve into the reasons why and how to prevent it.
Understanding Gasoline Degradation
Gasoline isn’t a static substance. It’s a complex mixture of hydrocarbons that are constantly changing, even when stored properly. Over time, gasoline undergoes a process called degradation, which significantly affects its performance and can damage your lawn mower’s engine.
The Chemistry of Stale Gas
The primary issue is the oxidation of gasoline. When exposed to oxygen, gasoline begins to break down, forming gum and varnish-like deposits. These deposits can clog the small passageways in your lawn mower’s carburetor, fuel lines, and fuel filter, restricting fuel flow and causing starting problems or poor engine performance.
Another crucial factor is the evaporation of volatile components. Gasoline is formulated with highly volatile compounds to ensure easy starting, especially in cold weather. As these components evaporate, the remaining gasoline becomes less flammable and harder to ignite, making it difficult to start your lawn mower.
Furthermore, the presence of ethanol in modern gasoline complicates the situation. Ethanol is added to gasoline for various reasons, including increasing octane and reducing emissions. However, ethanol is also hygroscopic, meaning it attracts and absorbs water from the atmosphere. This water can lead to phase separation, where the ethanol and water separate from the gasoline, forming a layer at the bottom of the fuel tank. This water-ethanol mixture is corrosive and can damage the fuel system components.
How Long Does Gasoline Last?
The lifespan of gasoline depends on several factors, including storage conditions, temperature, and the presence of ethanol. Generally, untreated gasoline can start to degrade within 30 days. After this period, you might notice a decrease in performance. After 3 to 6 months, the gasoline is likely to be too degraded to use effectively in your lawn mower. Gasoline with ethanol tends to degrade even faster, especially if exposed to moisture.
The Impact of Old Gas on Your Lawn Mower
Using old gas in your lawn mower can have several negative consequences, ranging from minor inconveniences to significant engine damage.
Starting Problems
One of the most common symptoms of using old gas is difficulty starting the lawn mower. The degraded fuel may not ignite properly, requiring excessive cranking or repeated attempts to start the engine.
Poor Engine Performance
Even if the lawn mower starts, old gas can cause poor engine performance. You might experience a loss of power, rough idling, sputtering, or stalling. The engine may struggle to maintain a consistent speed, especially when cutting thick grass.
Carburetor Clogging
The gum and varnish deposits formed by old gasoline can clog the carburetor’s jets and passages. The carburetor is responsible for mixing air and fuel in the correct ratio for combustion. If the carburetor is clogged, the engine won’t receive the proper fuel mixture, leading to performance problems.
Fuel System Damage
The corrosive effects of water and ethanol can damage fuel system components, such as fuel lines, fuel filters, and the fuel tank. These components may deteriorate, crack, or leak, requiring costly repairs or replacements.
Engine Damage
In severe cases, using old gas can lead to engine damage. If the engine runs lean (too much air and not enough fuel) due to a clogged carburetor, it can overheat and cause damage to the pistons, valves, and cylinder walls.
Prevention is Key: Protecting Your Lawn Mower from Old Gas
The best way to avoid the problems associated with old gas is to prevent it from occurring in the first place. Here are some practical tips to protect your lawn mower and ensure reliable performance.
Use Fresh Gasoline
Whenever possible, use fresh gasoline in your lawn mower. Purchase only the amount of gasoline you expect to use within a month or two. Avoid storing large quantities of gasoline for extended periods.
Add Fuel Stabilizer
Fuel stabilizers are additives that help prevent gasoline from degrading. They work by inhibiting oxidation, preventing the formation of gum and varnish, and stabilizing the fuel. Adding a fuel stabilizer to your gasoline can significantly extend its lifespan, allowing you to store it for longer periods without worrying about degradation. Follow the manufacturer’s instructions for the correct dosage.
Store Gasoline Properly
Proper storage is crucial for maintaining the quality of gasoline. Store gasoline in a clean, airtight container specifically designed for fuel storage. Keep the container in a cool, dry, and well-ventilated area, away from direct sunlight and heat sources. Avoid storing gasoline in humid environments, as moisture can accelerate degradation.
Drain the Fuel Tank Before Storage
If you plan to store your lawn mower for an extended period, such as over the winter, it’s best to drain the fuel tank completely. This will prevent the gasoline from degrading and causing problems when you start the lawn mower again in the spring. Run the engine until it stalls to ensure that all the fuel is removed from the carburetor and fuel lines.
Run the Engine Periodically
If you don’t drain the fuel tank, start the engine periodically during the storage period and let it run for a few minutes. This will help circulate the fuel and prevent it from stagnating in the carburetor.
Use Ethanol-Free Gasoline
If possible, use ethanol-free gasoline in your lawn mower. Ethanol-free gasoline is less prone to water absorption and degradation, making it a better choice for small engines. While it may be slightly more expensive, the benefits of using ethanol-free gasoline can outweigh the cost in the long run.
Reviving a Lawn Mower with Old Gas: What to Do
If you suspect that your lawn mower is suffering from the effects of old gas, here are some steps you can take to try and revive it.
Drain the Old Gas
The first step is to drain the old gas from the fuel tank. Use a siphon or drain plug to remove the fuel. Dispose of the old gas properly according to local regulations.
Clean the Carburetor
The carburetor is often the primary culprit when dealing with old gas problems. Cleaning the carburetor can remove gum and varnish deposits, restoring proper fuel flow.
- Remove the carburetor: Carefully disconnect the fuel lines, throttle linkage, and choke linkage.
- Disassemble the carburetor: Take apart the carburetor, removing the float bowl, jets, and other components.
- Clean the components: Use carburetor cleaner to thoroughly clean all the carburetor parts. Pay special attention to the jets, ensuring that they are free of any blockages. Use a small wire or carburetor cleaning tool to clear any stubborn clogs.
- Reassemble the carburetor: Put the carburetor back together, making sure all the parts are properly aligned and secured.
- Reinstall the carburetor: Reattach the fuel lines, throttle linkage, and choke linkage.
Replace the Fuel Filter
The fuel filter is designed to trap contaminants and prevent them from entering the carburetor. If the fuel filter is clogged with old gas deposits, it can restrict fuel flow. Replace the fuel filter with a new one to ensure a clean fuel supply.
Check the Spark Plug
A faulty spark plug can also cause starting problems. Remove the spark plug and inspect it for signs of fouling or damage. Clean the spark plug with a wire brush or replace it with a new one if necessary.
Add Fresh Gasoline and Fuel Stabilizer
Once you have cleaned the carburetor, replaced the fuel filter, and checked the spark plug, add fresh gasoline to the fuel tank along with a fuel stabilizer.
Attempt to Start the Engine
Try to start the engine. It may take several attempts to prime the fuel system and get the engine running smoothly. If the engine still doesn’t start, you may need to repeat the carburetor cleaning process or seek professional assistance.
When to Seek Professional Help
If you have tried the above steps and your lawn mower still refuses to start or runs poorly, it may be time to seek professional help from a qualified mechanic. They have the expertise and tools to diagnose and repair more complex engine problems.
Here are some situations where professional assistance is recommended:
- Severe engine damage: If you suspect that the engine has been damaged by old gas, such as a scored cylinder or damaged valves, a mechanic can assess the extent of the damage and recommend the appropriate repairs.
- Complex carburetor problems: If the carburetor is severely clogged or damaged, a mechanic may be able to rebuild or replace it.
- Fuel system issues: If you suspect that there are problems with the fuel pump, fuel lines, or fuel tank, a mechanic can diagnose and repair these issues.
Taking care of your lawn mower’s fuel system is crucial for ensuring reliable performance and prolonging its lifespan. By understanding the effects of old gas and taking preventative measures, you can avoid costly repairs and keep your lawn mower running smoothly for years to come.
| Problem | Possible Cause | Solution |
| ————————— | ——————————— | —————————————– |
| Hard to start | Old gas, clogged carburetor | Drain gas, clean/replace carburetor |
| Poor engine performance | Old gas, clogged fuel filter | Drain gas, replace fuel filter |
| Engine stalls frequently | Water in gas, clogged carburetor | Drain gas, clean/replace carburetor |
| Engine won’t start at all | Clogged fuel lines, bad spark plug | Check/replace fuel lines, replace spark plug |
Can old gas actually damage my lawn mower engine?
Yes, old gas can definitely damage your lawn mower engine. Gasoline begins to degrade over time, especially when exposed to air. This degradation leads to the formation of gums and varnishes that can clog fuel lines, carburetors, and other vital engine components. These deposits restrict fuel flow, making it difficult for the engine to start or run smoothly, and in severe cases, can cause irreversible damage.
Furthermore, ethanol-blended gasoline, common at most gas stations, absorbs water from the atmosphere. This water separation, known as phase separation, leaves you with a layer of water and ethanol at the bottom of your fuel tank and less effective gasoline at the top. This water can cause corrosion and further exacerbate engine problems, leading to costly repairs or even the need to replace the mower.
How long does gasoline typically remain “good” for use in a lawn mower?
Unstabilized gasoline typically remains usable in a lawn mower for only about 30 days. After this period, the volatile components start to evaporate, and the gasoline begins to break down, leading to the formation of harmful deposits. Environmental factors like temperature and humidity can accelerate this degradation process, further shortening the lifespan of the fuel.
However, using a fuel stabilizer can extend the life of gasoline significantly, potentially up to 12 months or even longer. Fuel stabilizers prevent the breakdown of gasoline and protect against the formation of gums and varnishes. Properly stored fuel, in a sealed container and a cool, dark place, will also last longer than fuel left in a lawn mower’s tank.
What are the signs that my lawn mower is running on stale gas?
Several signs indicate that your lawn mower might be running on stale gas. Difficulty starting the engine is a common symptom. You might also experience rough idling, sputtering, or stalling during operation. The engine may lack power and struggle to maintain a consistent RPM, even when under a light load.
Another telltale sign is a strong, unpleasant odor emanating from the fuel tank or exhaust. The fuel itself may appear darker than usual or have a gummy consistency. If you notice any of these symptoms, it’s best to drain the old fuel and replace it with fresh gasoline before attempting to operate the mower further.
Can I just add fresh gas to old gas to make it usable again?
While adding fresh gas to old gas might seem like a quick fix, it’s generally not recommended. While a small amount of old gas mixed with a larger quantity of fresh gas *might* allow the engine to run, it doesn’t eliminate the harmful effects of the degraded fuel. The old gas still contains gums and varnishes that can clog the carburetor and fuel lines.
Mixing fresh and old gas is essentially diluting the problem rather than solving it. The best approach is to completely drain the old gas from the tank and carburetor, and then refill with fresh, stabilized fuel. This ensures that your engine receives the clean, effective fuel it needs to operate optimally and avoids potential damage from the residual contaminants.
How should I properly store gasoline for my lawn mower to prevent it from going bad?
Proper gasoline storage is crucial for maintaining its quality and preventing degradation. Always store gasoline in a clean, airtight container specifically designed for fuel storage. These containers are typically made of plastic or metal and are designed to prevent vapor leakage and spills. Avoid using containers that have previously held other liquids, as contamination can negatively impact fuel quality.
Store the fuel container in a cool, dark, and well-ventilated area, away from direct sunlight and sources of heat. A garage or shed is usually a suitable location. Adding a fuel stabilizer to the gasoline before storage is highly recommended. This will help prevent the formation of gums and varnishes and extend the lifespan of the fuel significantly. Make sure to follow the instructions on the fuel stabilizer product for proper dosage.
What steps should I take if I suspect my lawn mower has been running on bad gas?
If you suspect your lawn mower has been running on bad gas, the first step is to drain the fuel tank completely. Dispose of the old fuel properly according to local regulations. Next, clean the carburetor to remove any gum or varnish deposits that may have accumulated. This can be done using carburetor cleaner, available at most auto parts stores.
After cleaning the carburetor and draining the fuel tank, replace the fuel filter to ensure that any remaining contaminants are removed from the fuel system. Finally, refill the tank with fresh, stabilized gasoline. Start the engine and allow it to run for a few minutes to ensure that the new fuel is flowing properly and that the engine is running smoothly. If problems persist, you may need to seek professional assistance from a qualified lawn mower repair technician.
Is there a difference between regular gasoline and premium gasoline when it comes to shelf life in a lawn mower?
Generally, there isn’t a significant difference in shelf life between regular and premium gasoline when it comes to lawn mower use. Both types of gasoline degrade over time and are susceptible to the same issues, such as the formation of gums and varnishes and phase separation in ethanol-blended fuels. The octane rating, which distinguishes premium from regular gasoline, doesn’t directly impact how quickly the fuel deteriorates.
The key factor influencing shelf life is the presence of ethanol and proper storage practices. Regardless of whether you use regular or premium gasoline, it’s crucial to use a fuel stabilizer and store the fuel in a sealed container in a cool, dark place to maximize its usability. Therefore, focusing on stabilization and storage is more important than the octane rating when considering fuel longevity for your lawn mower.