The hum of a well-maintained lawn mower is a familiar sound of summer for many homeowners. But what happens when that familiar sound is replaced by sputtering, choking, and a general refusal to start? More often than not, the culprit is old gasoline. Gas, especially the ethanol-blended variety common at most fuel stations, has a limited shelf life. Over time, it degrades, loses its combustibility, and can cause significant damage to your lawn mower’s engine. This article will guide you through identifying old gas, understanding its effects, and most importantly, what to do to get your mower running smoothly again.
Understanding the Lifespan of Gasoline
Gasoline is a volatile substance, and its quality deteriorates with time and exposure to air and moisture. While the exact lifespan can vary depending on storage conditions and fuel additives, most experts agree that gasoline begins to degrade noticeably after about 30 days. Ethanol-blended fuels, commonly found at gas stations in the United States, tend to have an even shorter shelf life, often becoming problematic after as little as 60 days.
Several factors contribute to this degradation. Oxygen in the air can react with the fuel, leading to oxidation. Water, which can condense in storage tanks or be absorbed from the atmosphere, can cause phase separation in ethanol-blended fuels. This means the ethanol, which is hygroscopic (attracts water), can separate from the gasoline and settle at the bottom of the tank, creating a corrosive mixture.
Identifying Old Gas in Your Lawn Mower
Recognizing the signs of old gas is crucial for preventing engine damage. The most obvious indicator is if your lawn mower simply won’t start or runs poorly. However, there are other clues you can look for before even attempting to start the engine.
Visually inspecting the fuel can sometimes reveal signs of degradation. Old gasoline may appear cloudy or discolored, often taking on a darker hue than fresh fuel. If you store gasoline in a translucent container, you might notice sediment at the bottom. This sediment can be a combination of degraded fuel components and rust from the storage container.
A distinct odor can also signal old gas. Fresh gasoline has a strong, sharp smell. Old gasoline, on the other hand, can sometimes smell stale, rancid, or even like varnish. This is due to the breakdown of fuel additives and the formation of new, less volatile compounds.
If you have a two-stroke engine (common in some string trimmers and older or smaller lawn mowers that require a gas-oil mix), old gas can be particularly problematic. The oil and gas can separate, leading to an improper fuel-oil ratio. This can cause severe engine damage due to inadequate lubrication.
The Negative Effects of Old Gas on Your Lawn Mower
Using old gas in your lawn mower can lead to a cascade of problems, ranging from minor performance issues to expensive engine repairs. Understanding these effects will underscore the importance of proper fuel management.
One of the most common issues is fuel system clogging. As gasoline degrades, it can form sticky, varnish-like deposits. These deposits can clog the fuel filter, fuel lines, and most importantly, the carburetor jets. The carburetor is the component responsible for mixing the correct amount of fuel and air for combustion. Even small clogs in its tiny passages can disrupt this delicate balance, leading to a no-start condition or poor engine performance.
Ethanol-related problems are also a significant concern with old gas. Ethanol can absorb water, leading to phase separation. This water-ethanol mixture is corrosive and can damage metal fuel tanks, fuel lines, and carburetor components, especially those made of rubber or plastic. It can also cause aluminum parts to corrode.
Old fuel can also lead to incomplete combustion. The octane rating of gasoline decreases as it ages, meaning it’s less resistant to knocking or pinging. This can result in reduced engine power, rough idling, and increased exhaust emissions. In severe cases, prolonged use of degraded fuel can lead to premature engine wear and even catastrophic engine failure.
Safely Disposing of Old Gasoline
The first and most crucial step when you have old gas in your lawn mower is to remove it. However, simply pouring it out onto the ground or down a drain is not an option. Gasoline is a hazardous material and must be disposed of properly to protect the environment and comply with local regulations.
The best way to dispose of old gasoline is to take it to a hazardous waste collection facility or a recycling center that accepts motor oil and fuels. Many local municipalities or counties have designated drop-off locations for household hazardous waste. You can usually find this information on your local government’s website or by calling your waste management services.
If you cannot immediately transport the old gas, store it in a properly sealed, approved gasoline container in a well-ventilated area, away from any ignition sources. Ensure the container is clearly labeled as “old gasoline” or “hazardous waste.”
Never mix old gasoline with fresh gasoline. This will contaminate the fresh fuel and potentially cause the same problems in your mower.
Emptying the Fuel Tank
Before you can dispose of the old gas, you need to remove it from your lawn mower’s fuel tank. There are a few methods for doing this, ranging from simple siphoning to using a dedicated fuel transfer pump.
The most common method is siphoning. You’ll need a length of clean, flexible tubing. Insert one end of the tubing into the fuel tank and the other end into an approved gasoline container. To start the siphoning process, you can either manually create suction by gently sucking on the end of the tube until fuel begins to flow (be careful not to ingest any fuel) or use a siphon pump. Many auto parts stores sell inexpensive hand-held siphon pumps designed for this purpose, which are much safer.
Alternatively, if your lawn mower has an accessible fuel drain plug, you can use that. Consult your lawn mower’s owner’s manual to see if it has a drain plug and its location. Place an approved gasoline container beneath the drain plug and carefully loosen it to allow the fuel to drain out. Be prepared to stop the flow quickly once the tank is empty or if you over-loosen the plug.
For smaller amounts of fuel, or if siphoning proves difficult, a small, battery-powered fuel transfer pump can be a useful tool. These pumps are designed to safely and efficiently move fuel from one container to another.
Cleaning the Fuel System Components
Once the old gas is removed, you’ll likely need to clean the fuel system components to remove any residual varnish or sediment. This is especially important if you suspect the old gas has caused any blockages.
Cleaning the Fuel Tank
If you suspect significant contamination or corrosion in the fuel tank, it’s best to clean it thoroughly. After emptying, you can rinse the tank with a small amount of fresh gasoline and then carefully pour it into an approved container for disposal. Some people also use a specialized fuel tank cleaner, following the product’s instructions carefully. Ensure the tank is completely dry before refilling with fresh fuel.
Cleaning the Fuel Lines and Filter
Fuel lines are usually flexible rubber or plastic hoses. If they appear gummy or clogged, they may need to be replaced. If they seem intact but potentially have internal residue, you can try flushing them with a small amount of carburetor cleaner or fresh gasoline. Always have a container ready to catch any excess fluid.
The fuel filter is a critical component that traps debris. If your mower has an external fuel filter, it’s often easiest to replace it with a new one. This is a relatively inexpensive part that can prevent a lot of future headaches. If your mower’s filter is integrated into the fuel line or tank, you might need to clean it according to the manufacturer’s recommendations.
Cleaning the Carburetor
The carburetor is often the most affected component by old gas. If your mower is running poorly or won’t start after emptying the tank and using fresh fuel, the carburetor likely needs cleaning. This can range from a simple spray-down to a complete disassembly and soaking.
For a basic cleaning, you can spray carburetor cleaner directly into the carburetor’s intake, typically where the air filter attaches, while the engine is trying to start or running. This can sometimes dissolve minor blockages.
A more thorough cleaning involves removing the carburetor from the engine. Disassemble the carburetor carefully, noting the position of each part. Soak the metal components in carburetor cleaner for several hours or overnight. Use compressed air and small brushes or wires to clear any blockages in the jets and passages. Reassemble the carburetor, ensuring all gaskets and seals are in good condition. If any parts appear damaged or excessively corroded, they should be replaced.
For many homeowners, especially those not mechanically inclined, taking the carburetor to a small engine repair shop for professional cleaning might be the most efficient and effective solution.
Refilling with Fresh Fuel and Adding Stabilizer
Once you’ve emptied the old gas and cleaned the fuel system, it’s time to refill your lawn mower with fresh fuel. Use gasoline with the octane rating recommended in your owner’s manual. For most lawn mowers, this is regular unleaded gasoline.
It’s also highly recommended to add a fuel stabilizer to the fresh gasoline. Fuel stabilizers are additives that help prevent fuel degradation, oxidation, and phase separation. They are particularly beneficial for small engines that are only used seasonally or intermittently. Follow the manufacturer’s instructions for the correct ratio of stabilizer to fuel.
If you know you won’t be using your lawn mower for an extended period (e.g., over winter), it’s best to either run the engine until all the fuel in the carburetor and fuel lines is consumed, or fill the tank completely with stabilized fuel. Filling the tank can help reduce condensation inside the tank, which contributes to water contamination. Running the engine dry ensures there’s no fuel to degrade in the carburetor.
Preventing Future Old Gas Problems
The best way to deal with old gas is to avoid having it in the first place. Implementing good fuel management practices can save you time, money, and frustration.
One of the simplest preventative measures is to buy only as much gasoline as you anticipate using in a month or two. Avoid filling up large gas cans if you only use your mower occasionally.
Store gasoline properly. Use only approved gasoline containers and keep them sealed tightly. Store them in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and ignition sources. Avoid storing gasoline in freezing temperatures, as this can also affect its quality.
Regularly use a fuel stabilizer. Add it to your gasoline at the time of purchase, especially if you don’t use your mower frequently. This is a small investment that can pay significant dividends in engine longevity.
Make it a habit to run your lawn mower dry at the end of each mowing season. This prevents old fuel from sitting in the carburetor and fuel lines over the winter months, which is a prime time for fuel to degrade. If running it dry isn’t feasible, always use stabilized fuel and consider draining the tank before storage.
Consider using ethanol-free gasoline if it is available in your area and your lawn mower manufacturer approves of its use. Ethanol-free gasoline has a much longer shelf life and is less prone to water absorption and phase separation. However, it can sometimes be more expensive and less readily available. Always check your owner’s manual before switching to ethanol-free fuel.
By understanding the nature of gasoline and adopting these preventative measures, you can ensure your lawn mower is always ready to tackle your yard work, starting with a clean tank and fresh, stabilized fuel.
What is considered “old gas” for a lawn mower?
Old gas in a lawn mower typically refers to gasoline that has been stored for an extended period, generally longer than 30 days. Over time, gasoline degrades due to oxidation and evaporation of its lighter, more volatile components. This process can lead to gum and varnish formation, which can clog fuel lines and carburetor jets.
The shelf life of gasoline can vary depending on storage conditions. Factors like temperature, exposure to air, and the presence of ethanol can significantly impact how quickly it deteriorates. Storing gas in a sealed, approved container in a cool, dry place can help prolong its usability, but even under ideal conditions, it’s not meant for indefinite storage.
What are the potential problems caused by using old gas in a lawn mower?
Using old gas can lead to a range of performance issues for your lawn mower. The most common problems include difficulty starting, rough idling, stalling, loss of power, and an inability to reach full throttle. This is primarily due to the degraded fuel not combusting efficiently and the formation of deposits that impede fuel flow.
More serious consequences can arise from prolonged use of old gas. The gummy residue can permanently damage or clog the carburetor, requiring a costly repair or replacement. It can also lead to corrosion within the fuel system components, potentially causing leaks or other mechanical failures.
How can I safely dispose of old lawn mower gas?
Safely disposing of old lawn mower gas is crucial for environmental protection and to prevent hazards. Never pour old gasoline down a drain, onto the ground, or into regular trash. Instead, collect the old fuel in a sealed, approved gasoline container.
The best method for disposal is to take it to a local hazardous waste collection facility or a service station that accepts used gasoline. Many auto parts stores also have collection programs for hazardous fluids. Always check with your local municipality or waste management services for specific guidelines and drop-off locations in your area.
Can I add fresh gas to old gas to “revive” it?
Adding a small amount of fresh gasoline to old gasoline will not effectively “revive” it or prevent the problems associated with degraded fuel. While it might slightly dilute the contaminants, the old gasoline’s harmful gum and varnish will still be present and can cause issues.
For best results, it’s recommended to either drain all the old gas and replace it with fresh fuel or use a fuel stabilizer in the old gas if you intend to store it for a short period. If the gas is significantly old and degraded, it’s always safer to dispose of it properly.
What is a fuel stabilizer and how does it help with old gas?
A fuel stabilizer is an additive that is mixed with gasoline to prevent its degradation during storage. It works by slowing down the oxidation process, which is the primary cause of gasoline breakdown. Stabilizers also help to prevent phase separation, especially in fuels containing ethanol, where water can separate from the gasoline.
By using a fuel stabilizer, you can significantly extend the shelf life of gasoline, making it safe to use in your lawn mower for much longer periods, often up to a year or more. It’s an excellent preventative measure if you know you won’t be using all the gas you purchase or if you’re storing your mower for the winter.
How do I drain the old gas from my lawn mower?
Draining old gas from your lawn mower involves a few key steps to ensure safety and effectiveness. First, ensure the mower is on a level surface and that the engine is cool. Locate the fuel tank and, if there’s a shut-off valve, close it.
There are a couple of common methods for draining. You can use a siphon pump to transfer the gas from the tank into an approved container. Alternatively, you might be able to unscrew the carburetor bowl drain screw to let the gas out directly, but be prepared to catch the fuel in a suitable container. Always wear gloves and eye protection.
Should I clean the fuel system after using old gas?
It is highly recommended to clean the fuel system after using old gas, especially if you experienced performance issues or if the gas was particularly old and degraded. The old gas can leave behind sticky residues and gum that can clog fuel lines, the fuel filter, and especially the carburetor.
Cleaning might involve flushing the fuel tank with fresh gasoline, replacing the fuel filter, and potentially cleaning or rebuilding the carburetor. If you’re unsure about the process, consulting your lawn mower’s manual or seeking professional assistance from a small engine repair shop is a wise decision to prevent further damage.