Why Is My Lawn Mower Blowing Grey Smoke? Common Causes and Solutions

Is your lawn mower smoking grey? If so, you’re not alone. It’s a common problem that can be caused by a variety of factors. Understanding the reasons behind your lawn mower blowing grey smoke is crucial in maintaining its performance and longevity. In this article, we will explore the common causes of this issue and provide practical solutions to help you get your lawn mower back on track.

From engine problems to fuel issues, there are several potential culprits for grey smoke emissions from your mower. By identifying the root cause and taking appropriate action, you can ensure that your lawn mower operates efficiently and effectively. Whether you are a homeowner with a small yard or a landscaping professional, understanding the reasons behind grey smoke will empower you to tackle the issue with confidence.

Key Takeaways
Grey smoke coming from a lawn mower usually indicates an oil leak or burning oil. This could be caused by overfilling the oil reservoir, a damaged piston ring, or a clogged breather tube. It’s important to address the issue promptly to prevent further damage to the engine. Checking the oil level and ensuring proper maintenance of the mower can help resolve the problem. If the issue persists, it’s advisable to seek professional assistance for repairs.

Clogged Air Filter

When your lawn mower is blowing grey smoke, a common culprit is a clogged air filter. The air filter prevents dirt, debris, and other particles from entering the engine and causing it to run inefficiently. However, over time, the filter can become clogged with dirt and grass clippings, restricting the airflow to the engine. This can lead to a rich air-fuel mixture, causing the grey smoke to be emitted from the exhaust.

To resolve this issue, start by locating the air filter, typically found near the carburetor or under a cover on the side of the engine. Remove the filter and inspect it for dirt and debris. If it appears dirty, use a brush or compressed air to clean it thoroughly. For heavily clogged filters, consider replacing it with a new one to ensure proper airflow to the engine.

Regularly checking and cleaning or replacing the air filter as part of your lawn mower maintenance routine can prevent the issue of grey smoke and help keep your mower running smoothly. By maintaining a clean air filter, you can ensure proper engine performance and reduce the risk of grey smoke emissions.

Overfilled Oil Reservoir

Overfilling the oil reservoir in your lawn mower can lead to grey smoke emanating from the exhaust. When the oil reservoir is overfilled, the excess oil can seep into the combustion chamber and cause the engine to burn off the excess oil. This can result in grey smoke being emitted from the exhaust as the oil burns alongside the fuel.

To resolve this issue, it is crucial to drain the excess oil from the reservoir to the recommended level as specified in the lawn mower’s manual. Ensure that the mower is on level ground when checking and adjusting the oil level. It is also important to use the correct type and grade of oil as recommended by the manufacturer to prevent overfilling in the future. Regularly monitor the oil level to prevent overfilling and ensure proper engine performance.

Overfilling the oil reservoir in a lawn mower can lead to performance issues and potential damage to the engine. Therefore, it is essential to adhere to the manufacturer’s guidelines for oil levels and maintenance to keep your lawn mower running smoothly and efficiently.

Damaged Piston Rings

When a lawn mower’s piston rings are damaged, it can lead to the emission of grey smoke. The piston rings are responsible for sealing the combustion chamber, and when they are worn or damaged, oil can leak into the combustion chamber and produce grey smoke during operation. This can be due to wear and tear over time or improper maintenance, such as infrequent oil changes or the use of low-quality oil.

To address this issue, the damaged piston rings will need to be replaced. This typically involves disassembling the engine to access the piston rings, which can be a complex and time-consuming task. Therefore, it is often best left to experienced professionals. Additionally, regular maintenance, including using the recommended oil and changing it at the specified intervals, can help prevent premature wear of the piston rings and prolong the life of the lawn mower’s engine.

In summary, damaged piston rings can be a common cause of grey smoke emission from a lawn mower. Proper maintenance and timely replacement of worn piston rings can help resolve this issue and ensure the efficient operation of the lawn mower.

Worn-Out Valve Seals

One common cause of grey smoke coming from a lawn mower is worn-out valve seals. Valve seals are responsible for controlling the flow of oil into the combustion chamber. If these seals become worn or damaged, excess oil can leak into the combustion chamber, leading to grey smoke emissions during operation.

In order to address this issue, it is important to inspect the valve seals for signs of wear or damage. If the valve seals are found to be worn-out, they will need to be replaced. This typically involves disassembling the engine and removing the cylinder head to access the seals. Once the worn-out seals are replaced, the engine should no longer produce grey smoke during operation.

Regular maintenance, such as checking and replacing worn-out valve seals, can help ensure the optimal performance and longevity of a lawn mower. By addressing this issue promptly, mower owners can prevent further damage and enjoy a cleaner, more efficient operation of their equipment.

Fuel Mixture Imbalance

One common cause of a lawn mower blowing grey smoke is a fuel mixture imbalance. When the fuel mixture in the lawn mower’s engine is not properly balanced, it can lead to a rich fuel mixture, which produces grey smoke. This imbalance may occur if there is too much oil in the fuel, resulting in incomplete combustion.

To address this issue, start by checking the fuel mixture in the lawn mower. Ensure that the fuel and oil are mixed according to the manufacturer’s guidelines. If the mixture is too rich, drain the fuel tank and carburetor, then refill it with the correct fuel-to-oil ratio. Additionally, it’s important to clean or replace the air filter and spark plug to ensure proper airflow and spark ignition, which can contribute to a balanced fuel mixture.

Regular maintenance and following the recommended fuel-to-oil ratio can prevent fuel mixture imbalance and the related grey smoke emissions from your lawn mower. If the issue persists after adjusting the fuel mixture, it may be necessary to consult a professional for further diagnosis and repair.

Faulty Spark Plug

A faulty spark plug can also cause your lawn mower to blow grey smoke. If the spark plug is dirty or fouled, it may not produce a strong enough spark to ignite the fuel-air mixture properly. This can result in incomplete combustion, leading to the appearance of grey smoke.

To rectify this issue, start by removing the spark plug and inspecting it for signs of damage, fouling, or corrosion. If the spark plug is dirty, it can be cleaned using a wire brush and sprayed with a spark plug cleaner to remove any built-up deposits. If the spark plug is damaged or excessively worn, it should be replaced with a new one to ensure proper ignition.

Additionally, it’s important to check that the spark plug is correctly gapped according to the manufacturer’s specifications. Improperly gapped spark plugs can also cause ignition problems and lead to grey smoke emissions. By maintaining a clean and properly functioning spark plug, you can ensure that your lawn mower’s engine is firing efficiently and reduce the likelihood of grey smoke being emitted during operation.

Engine Overheating

Engine Overheating:

One common cause of grey smoke from a lawn mower is engine overheating. When the engine runs at excessively high temperatures, it can lead to the production of grey smoke. This can occur due to a variety of reasons, such as a lack of proper airflow causing the engine to overheat, dirty air filters restricting airflow, or a malfunctioning cooling system.

To resolve the issue of engine overheating, it is important to ensure that the lawn mower is receiving proper airflow. Clean or replace dirty air filters and inspect the cooling system for any malfunctions. Additionally, regularly checking the oil level and ensuring it is at the correct level can also help prevent engine overheating. If the issue persists, it may be necessary to seek professional help to diagnose and repair any underlying mechanical problems causing the engine to overheat and produce grey smoke. Regular maintenance and attention to these factors can help prevent engine overheating and the associated grey smoke, ensuring optimal lawn mower performance.

Professional Maintenance Tips

For professional maintenance tips, it’s essential to have your lawn mower serviced annually by a qualified technician. A professional can conduct a thorough inspection of the engine, air filter, spark plug, and exhaust system. They can also check for any oil leaks, clean or replace the carburetor, and ensure all parts are properly lubricated. Additionally, they can adjust the throttle and choke settings and inspect the fuel system for any clogs or issues.

Moreover, regular maintenance, such as changing the oil and air filter, cleaning the cutting blades, and keeping the mower free of debris, can significantly extend its lifespan and improve performance. A professional can offer specific recommendations based on the model and usage of your lawn mower, helping you maximize its efficiency and reduce the likelihood of it emitting grey smoke. Regular professional maintenance not only keeps your lawn mower running smoothly but can also prevent potential issues that may lead to grey smoke emission.


In addressing the issue of a lawn mower blowing grey smoke, it is essential to understand the common causes and solutions in order to maintain the optimal performance of the equipment. By recognizing the potential reasons behind the grey smoke emission, such as overfilling, worn-out parts, or poor fuel quality, individuals can take proactive steps to rectify the problem and prevent further damage. Regular maintenance, including routine inspection and timely replacement of faulty components, will not only prolong the lifespan of the lawn mower but also ensure efficient and eco-friendly operation.

In conclusion, being aware of the common causes and solutions for a lawn mower emitting grey smoke empowers users to effectively troubleshoot and rectify the issue. By implementing the recommended solutions and adhering to a diligent maintenance routine, individuals can enjoy a well-functioning and smoke-free lawn mower, ultimately contributing to a healthier outdoor environment.

Leave a Comment