Gasoline is the lifeblood of your lawn mower, enabling it to power through your yard work. But like any fuel, it doesn’t last forever. Understanding how long gas can sit in your lawn mower before it degrades and causes problems is crucial for maintaining your equipment and preventing costly repairs. This article delves into the factors that affect fuel degradation, the signs of bad gas, and preventative measures you can take to keep your lawn mower running smoothly.
The Science Behind Fuel Degradation
Gasoline isn’t a simple, uniform substance. It’s a complex mixture of hydrocarbons, and its composition makes it susceptible to degradation over time. Several factors contribute to this process.
Oxidation: The Silent Thief
One of the primary culprits in fuel degradation is oxidation. When gasoline is exposed to air, it reacts with oxygen, leading to the formation of gums and varnishes. These sticky substances can clog fuel lines, carburetors, and other vital engine components, hindering performance and causing starting problems. The rate of oxidation increases with temperature and exposure to air, making proper storage essential.
Evaporation: Losing Volatile Components
Gasoline is designed with a specific blend of volatile components that allow it to ignite easily and provide efficient combustion. Over time, these volatile components evaporate, reducing the fuel’s octane rating and making it harder to start the engine. This evaporation is particularly pronounced in warmer climates and in vented fuel tanks.
Ethanol’s Role: A Double-Edged Sword
Most gasoline sold today contains ethanol, an alcohol-based additive that enhances octane and reduces emissions. However, ethanol can also contribute to fuel degradation. Ethanol is hygroscopic, meaning it readily absorbs water from the atmosphere. This water contamination can lead to phase separation, where the ethanol and water separate from the gasoline, forming a corrosive layer at the bottom of the fuel tank. This layer can damage fuel system components and cause engine misfires. Furthermore, ethanol can degrade rubber and plastic components in older lawn mowers, leading to leaks and further fuel system problems.
Recognizing the Signs of Bad Gas
Identifying bad gas early can save you a lot of headaches and prevent damage to your lawn mower. Here are some telltale signs to watch out for:
Difficulty Starting the Engine
One of the most common signs of bad gas is difficulty starting the engine. If your lawn mower cranks but fails to start, or starts only after repeated attempts, stale fuel could be the culprit. The degraded fuel may not have the necessary volatility to ignite properly, making it difficult for the engine to get going.
Rough Idling or Stalling
If your lawn mower starts, but idles roughly or stalls frequently, it could be another indication of bad gas. The gums and varnishes formed by oxidation can clog the carburetor jets, disrupting the fuel-air mixture and causing the engine to run erratically.
Loss of Power
Stale fuel can also lead to a noticeable loss of power during operation. If your lawn mower struggles to cut through thick grass or bogs down under load, it may not be receiving the proper amount of fuel due to clogged fuel lines or a dirty carburetor.
Unusual Odor
Fresh gasoline has a distinct odor. If the fuel in your lawn mower smells stale, sour, or has a varnish-like odor, it’s likely that it has degraded and should be replaced.
Visible Debris or Discoloration
Inspect the fuel in your fuel tank. If you see visible debris, sediment, or discoloration, it’s a clear sign that the fuel has gone bad. Phase separation, caused by water contamination, will appear as a distinct layer at the bottom of the tank.
How Long Does Gas Last in a Lawn Mower?
The lifespan of gasoline in a lawn mower depends on several factors, including the type of gasoline, storage conditions, and the presence of ethanol.
Regular Gasoline vs. Premium Gasoline
Premium gasoline, with its higher octane rating, doesn’t necessarily last longer than regular gasoline. The degradation process is primarily driven by oxidation, evaporation, and water absorption, which affect both types of fuel equally.
The Impact of Ethanol Content
Gasoline containing ethanol tends to degrade faster than ethanol-free gasoline. Ethanol’s hygroscopic nature accelerates water absorption, leading to phase separation and corrosion. If possible, use ethanol-free gasoline in your lawn mower, especially if you plan to store it for extended periods.
Storage Conditions: A Critical Factor
The way you store your lawn mower and gasoline significantly impacts how long the fuel will last. Storing your lawn mower in a cool, dry place away from direct sunlight will help slow down the degradation process. Keep the fuel tank as full as possible to minimize the amount of air inside, reducing oxidation.
General Guidelines for Fuel Lifespan
As a general rule of thumb, gasoline can last anywhere from 3 to 6 months in a lawn mower if left untreated. However, this timeframe can vary depending on the factors mentioned above. Ethanol-blended gasoline may start to degrade in as little as 30 days.
Preventative Measures: Extending Fuel Life
Taking preventative measures can significantly extend the life of gasoline in your lawn mower and prevent fuel-related problems.
Using a Fuel Stabilizer
A fuel stabilizer is a chemical additive that helps prevent oxidation, evaporation, and water absorption. Adding a fuel stabilizer to your gasoline can extend its lifespan to 12 months or longer. Follow the manufacturer’s instructions for the correct dosage.
Choosing Ethanol-Free Gasoline
Whenever possible, use ethanol-free gasoline in your lawn mower. This will eliminate the risk of phase separation and corrosion, significantly extending the fuel’s lifespan.
Proper Storage Practices
Store your gasoline in a clean, airtight container in a cool, dry place away from direct sunlight. Ensure that the container is specifically designed for gasoline storage and is properly vented.
Emptying 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 empty the fuel tank completely. This will prevent the fuel from degrading and causing problems when you start the engine again in the spring. You can also run the lawn mower until it stalls to ensure that the carburetor is empty of fuel.
Regular Maintenance
Regular maintenance, including cleaning the carburetor and fuel lines, can help prevent fuel-related problems. Check your lawn mower’s owner’s manual for specific maintenance recommendations.
Dealing with Bad Gas
If you suspect that your lawn mower has bad gas, here’s how to address the problem:
Drain the Fuel Tank
The first step is to drain the fuel tank completely. Dispose of the old gasoline properly, following local regulations. Do not pour it down the drain or onto the ground.
Clean the Fuel System
After draining the fuel tank, clean the fuel system to remove any gums, varnishes, or debris. This may involve cleaning the carburetor, fuel lines, and fuel filter.
Replace the Fuel Filter
The fuel filter is designed to trap contaminants and prevent them from entering the engine. If you suspect that your lawn mower has bad gas, it’s a good idea to replace the fuel filter.
Refill with Fresh Gasoline
Once you’ve cleaned the fuel system and replaced the fuel filter, refill the fuel tank with fresh gasoline and a fuel stabilizer.
Start the Engine
After refilling the fuel tank, try starting the engine. It may take a few attempts to get the fuel flowing through the system, but the engine should eventually start and run smoothly. If the engine still doesn’t start or runs poorly, you may need to take it to a qualified mechanic for further repairs.
Long-Term Storage Considerations
Storing a lawn mower properly for extended periods, like over the winter, requires special attention to the fuel system.
Stabilizing the Fuel
Add a fuel stabilizer to the gasoline in the tank before storage, even if you plan to empty the tank. This helps protect the fuel system components from corrosion and deposits.
Draining the Carburetor
Even with a fuel stabilizer, it’s best to drain the carburetor to prevent fuel from evaporating and leaving behind sticky residues. Locate the drain screw on the carburetor and loosen it to allow the fuel to drain completely.
Applying Fogging Oil
Fogging oil is a special lubricant that protects the internal engine components from rust and corrosion during storage. Remove the spark plug and spray fogging oil into the cylinder, then pull the starter cord a few times to distribute the oil. Replace the spark plug.
By understanding the factors that affect fuel degradation and taking preventative measures, you can keep your lawn mower running smoothly for years to come.
How long can gasoline typically sit in a lawn mower before it starts to go bad?
Gasoline’s degradation timeline in a lawn mower depends on several factors, but generally, untreated gasoline starts to degrade within 30 to 60 days. This degradation primarily involves the lighter, more volatile components of the gasoline evaporating, leaving behind a thicker, less combustible residue. Ethanol, often blended with gasoline, also attracts moisture, accelerating the breakdown process and potentially leading to rust and corrosion in the fuel system.
After about 3 months, you’ll likely notice performance issues with your lawn mower. These issues can range from difficulty starting to rough idling and reduced power. Leaving gasoline untreated for longer periods, such as 6 months or more, can result in significant fuel system problems, requiring professional cleaning or even parts replacement. Using stale gasoline is a common cause of small engine problems, so it’s best to avoid it whenever possible.
What are the signs of bad gasoline in a lawn mower?
Several telltale signs indicate that the gasoline in your lawn mower has gone bad. Difficulty starting is often the first and most noticeable symptom. The engine may crank repeatedly without firing, or it might start briefly and then stall. Additionally, you might experience rough idling, where the engine sputters and struggles to maintain a consistent RPM.
Other signs include reduced engine power during operation. Your lawn mower might struggle to cut through grass, especially thicker patches. You might also notice a distinctive sour or varnish-like odor coming from the fuel tank or exhaust. Finally, visual inspection might reveal discolored gasoline or sediment at the bottom of the fuel tank, further confirming that the gasoline has deteriorated.
How does ethanol in gasoline affect its shelf life in a lawn mower?
Ethanol, a common additive in gasoline, significantly impacts its shelf life when used in lawn mowers. Ethanol is hygroscopic, meaning it readily absorbs moisture from the air. This absorbed water can lead to phase separation, where the ethanol and water separate from the gasoline, forming a distinct layer. This layer is highly corrosive and can damage fuel system components.
Furthermore, ethanol can degrade rubber and plastic parts commonly found in lawn mower fuel systems. This degradation can lead to leaks and clogs, causing engine performance issues. To mitigate these problems, it is recommended to use ethanol-free gasoline or add a fuel stabilizer specifically formulated to combat the effects of ethanol. Regular use of a stabilizer will extend the life of the gasoline and protect the engine.
What is a fuel stabilizer and how does it help extend the life of gasoline in a lawn mower?
A fuel stabilizer is a chemical additive designed to prevent the degradation of gasoline during storage. It works by inhibiting oxidation, which is the primary process that causes gasoline to break down and form gums and varnishes. Fuel stabilizers also contain detergents that help keep the fuel system clean and prevent the build-up of deposits.
When added to gasoline according to the manufacturer’s instructions, a fuel stabilizer can extend the shelf life of the fuel to as long as 12 to 24 months. This is especially important for lawn mowers that are stored for extended periods during the off-season. Using a fuel stabilizer can save you time and money by preventing costly repairs due to fuel-related issues.
What are the best practices for storing gasoline for lawn mowers to prevent it from going bad?
Proper storage is crucial for maintaining the quality of gasoline intended for lawn mowers. Start by using an approved gasoline container, typically red in color and designed to vent properly. Fill the container to about 95% capacity to allow for expansion and contraction due to temperature changes. Store the container in a cool, dry, and well-ventilated area away from direct sunlight and sources of heat or ignition.
Before storing the gasoline, add a fuel stabilizer to the container according to the manufacturer’s instructions. Mix the fuel stabilizer thoroughly by shaking the container. If possible, use ethanol-free gasoline, especially for long-term storage. Label the container with the date of purchase and the date the fuel stabilizer was added. Following these practices will significantly prolong the life of the gasoline and prevent fuel-related problems in your lawn mower.
Is it better to drain the gasoline from a lawn mower before storing it for the winter?
Draining the gasoline from a lawn mower before storing it for the winter is generally recommended. This prevents the gasoline from degrading and causing problems in the fuel system over the long off-season. Stale gasoline can leave behind varnish and gum deposits that can clog fuel lines, carburetors, and other engine components.
If you choose not to drain the fuel tank, ensure you add a fuel stabilizer to the gasoline and run the engine for a few minutes to circulate the treated fuel throughout the system. However, draining the tank provides the most complete protection against fuel-related issues. When draining, dispose of the gasoline properly according to local regulations. Starting with fresh fuel in the spring will ensure optimal engine performance.
Can old or bad gasoline damage a lawn mower engine? If so, how?
Yes, using old or bad gasoline can definitely damage a lawn mower engine. As gasoline degrades, it forms varnish and gum deposits. These deposits can clog fuel lines, carburetors, and fuel injectors, restricting the flow of fuel to the engine. This can lead to starting problems, rough idling, reduced power, and even engine stalling.
Furthermore, the water absorbed by ethanol-blended gasoline can cause corrosion and rust within the fuel system. This corrosion can damage fuel tank linings, fuel pumps, and other critical components. Over time, the accumulated damage from using bad gasoline can lead to costly repairs or even the need for engine replacement. Therefore, always use fresh, stabilized gasoline to protect your lawn mower engine and ensure its longevity.