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Why is oil coming out of the lawnmower’s exhaust?

Notice something odd with your lawnmower? Oil appearing in the exhaust is a sign that something’s not right. Our knowledge and experience can help you understand why this happens and how to fix it.

Oil can leak from a lawnmower’s exhaust if tilted, the oil reservoir is overfilled, the air filter is clogged, the carburetor is faulty, engine valves are worn, or internal issues like blown gaskets. Regular maintenance and repair of faulty parts can prevent oil from leaking out of the exhaust.

Are you puzzled by the oil in your lawnmower’s exhaust? Not sure what’s causing it or how to fix it? We’re here to help. Keep reading to gain a better understanding.


Steps to follow:

The oil can come out of the lawnmower exhaust for various reasons. It can be any technical fault or some other issue. Some of the problems are very simple, and some are very serious and very harmful as well. These severe issues also require some complicated repairs.

Following are some steps that need to be followed if the oil comes out of the lawn mower’s exhaust.

Step 1: Don’t tilt the lawnmower greater than 15 degrees

If you list your mower greater than fifty degrees, the mower’s oil crankcase may leak and move toward the carburetor. This may cause the lawn mower’s oil to come out of the exhaust.

It mostly happens when riding on a hill, incorrectly tilting the lawn mower, and the oil will flow toward the carburetor and then out of the exhaust.

Step 2: Squeeze the excess oil from the foam air filter

On the other hand, overfilling your lawn mower is another cause for the oil to come out of the exhaust. The lawnmower’s crankcase is very small if it needs less than 1 quart of oil to be filled. If it is overfilled, the oil can move anywhere. It can move towards the air filter, carburetor, or the cylinder.

So, if the crankcase is crammed, the overfilled oil can come out of the exhaust. Very little oil should be added to prevent spillage from incorrectly tilting the mower.

Step 3: Repair or replace the Clogged Air Filter

If the air filter is clogged, some of the fuel has remained unburnt. It will not allow the air to pass through the piston, so some of the power will remain unproduced. The air filter is a foamy structure that blocks impurities like dirt, debris, and insects.

If it has become porous or faulty, adequate air doesn’t pass through. This is the actual reason behind improper fuel combustion. You need to clean the filter to solve the issue. Otherwise, the unburnt fuel will cause the oil to leak along with the fuel residuals.

In my two decades of experience, I’ve found that oil in a lawnmower’s exhaust often stems from common issues such as a tipped or overfilled engine, a worn-out piston ring, or a malfunctioning head gasket.

Step 4: Adjust the Carburetor

The carburetor is an essential part of the lawnmower. If it is not working correctly, the carburetor will also face issues. You should keep your carburetor adjusted because if the carburetor is not changed, the fuel fails to burn.

This unburnt fuel will come out of the exhaust. The carburetor needs to be adjusted to solve this issue.

Step 5: Check the Muffler

The fluid coming out of the muffler is most commonly the unburnt fuel. If the carburetor is unadjusted, the power remains unburnt. On the other hand, if the air filter is clogged, the energy will remain unburnt. This unburnt fuel ejects out of the exhaust system.

If the liquid from the muffler smells like gas, then this problem is known as flooding. The muffler needs to be repaired or replaced to stop flooding.

Step 6: Replace the worn valves

 Valves are used in the cylinders of the lawnmowers to seal them properly to avoid any leakage. The cylinder will not be adequately filled if these valves are worn out. As a result, the oil will leak from the cylinder and come out through the exhaust. Therefore, replace the worn valves.

Step 7: Fixing Internal Problems

The engine can have some internal problems due to the oil leaking from the exhaust. Some of them may include:

  • Blown head gaskets: The heads of the engines are blocked by the head gaskets. The oil may move to the exhaust if these are not appropriately secured. If these gaskets are damaged, the oil will move towards the exhaust and come out of the seal.
  • Cracked Engine Block: Cracking of the engine blocks causes leakage. If the engine blocks are broken, the oil will leak from them.

Step 8: Check if the oil is bad

The oil that comes out of the engine and then from the exhaust may cause some issues. The following are some:

  1. White smoke: The oil coming out of the engine interacts with the other components and then produces white smoke. This smoke can be hazardous for the environment and your lungs as well. In this case, the oil needs to be replaced, and the filter needs to be cleaned.
  2. Dead Grass: The oil that leaks soaks into the grass. The soil is damaged, and it will produce dead grass. This will be very rough and will not look beautiful. Make sure to replace the oil promptly and clean the grass filter, too.

Frequently asked questions:

1. How do you prevent oil from leaking into the engine?

If you want your lawnmower to work correctly for a more extended period, you must maintain it properly. Proper maintenance allows the lawnmower to work appropriately for a more extended period.

2. Should I take a lawnmower to the shop if I notice oil in the exhaust?

Oil in the exhaust can be due to faulty filters, low-quality fluids, or rough operating conditions. You may call a professional if you don’t know how to fix the issues.

3. What causes the gas to come out of the exhaust?

This is due to the excess fuel. On the other hand, a leaking fuel injector may also be the reason. The unburnt energy comes out of the exhaust.

4. How do you check the oil level of the lawnmower?

The dipstick should check the oil level. Firstly you should remove and clean it with a cloth. Secondly, place the dipstick back into the mower. Now, check where the oil comes from. If it reaches the top, then it is filled. But if it is more than that, it may cause some issues.


The lawnmower needs proper maintenance to work correctly. On the other hand, if it is not maintained correctly, you may face the issues mentioned above. It is pretty frustrating, too, and can be costly sometimes.

The above-mentioned are the potential causes of why oil comes out of lawn mower exhaust. If you face the same issue, you must adequately consider the causes and solutions.

We have explained an easy fix to your problem that you can do yourself. However, if you are confused about what to do, take your lawnmower to a repair shop or call a professional.

If oil leakage is not addressed promptly, it can lead to engine damage, reduced performance, and potentially even engine failure, which I’ve unfortunately seen happen in my 20 years in the field

Don’t try to do it yourself if you don’t know exactly what to do. It would help if you also took care of the safety precautions while repairing anything.

If your lawnmower faces the above issues, follow the steps given above. This will help you fix your problem by yourself quite quickly. To make your lawn look more beautiful, you need the proper lawnmower.

So, it would be best to take great care of lawnmowers and their maintenance. This will allow your lawnmower to run correctly for a more extended period.

The Risk of Extreme Tilting in a Riding Lawn Mower

When mowing on a slope or performing maintenance, you must exercise caution to avoid an extreme tilt. Extreme tilting of the lawnmower leads the oil to leak from the crankcase and move toward the carburetor.

This event contributes to the issue of oil coming out of the exhaust on a lawnmower. A well-informed mower operator will appreciate this significance and avoid over-tilting their equipment.

• The Pitfalls of Overfilling Lawnmower Oil

The balance of oil in your lawnmower is vital. If it is too little, your engine may lack lubrication. Surprisingly, overfilling the oil reservoir can be equally damaging. Overfilling causes the oil to overflow and enter the air filter, carburetor, or cylinder, causing visible oil leaks from the exhaust.

Regular checks and maintaining oil at appropriate levels become crucial. Briggs & Stratton, a leading lawnmower manufacturer, provides further insights where required.

• Be Mindful of a Clogged Air Filter

Ensuring a clean, functional air filter is a relatively straightforward maintenance task that is often overlooked. A clogged air filter restricts airflow to the lawnmower engine, yielding more than decreased performance.

This obstruction can result in unburnt fuel and oil being expelled from the exhaust, demonstrating the importance of a clean air filter.

• Watch Your Lawnmower’s Carburetor

The carburetor is a critical component of any lawnmower. An imbalanced one can cause your fuel to burn inadequately, resulting in oil presence in the exhaust. Regularly checking your lawnmower carburetor can save you from this issue.

• Signs of Worn-Out Valves

The engine valves are practically the gatekeepers of your engine. Worn valves can lead to them failing to seal the cylinders properly, causing exhaust leaks. Regular inspection can catch worn valves early, saving you a significant repair bill.

• Effects of Internal Engine Problems

Many internal issues within the lawnmower engine, like blown head gaskets or cracked engine blocks, can contribute to oil leaks from the exhaust. Annual professional servicing or knowledge of internal parts handling can prevent such costly problems.

• The Aftermath of Oil Leak – White Smoke and Dead Grass

I suspect an oil leak, but I am unsure. Two tell-tale signs exist to confirm your suspicion. The appearance of white smoke and dead grass are potential issues originating from oil coming out of the exhaust. These are indicators that the oil may need replacing, the grass filter cleaning, and essential maintenance.

• The Power of Proper Maintenance

It’s easier to prevent problems than to solve them. Regular, proper maintenance is your key to prevent oil leaks. However, if matters get complex or you are uncertain about handling a problem, don’t hesitate to seek professional help.

Simple prevention methods can save you from many potential problems, including oil emissions from your lawnmower’s exhaust.

• Oil Leakage in Lawn Mowers: A Threat to Components

It’s a common sight for an experienced lawn mower operator like myself: oil leaking from your machine’s exhaust.

You might dismiss this as an insignificant wear and tear aspect on superficial examination. However, it’s essential to understand the extent of damage this can inflict on your reliable lawn mower.

One of the primary components at risk is your spark plugs. These are crucial for igniting the air-fuel mixture in your mower’s engine. Oil leakage, if ignored, contaminates these spark plugs, compromising their performance.

Another component adversely affected by oil leakage is air filters. Their primary responsibility is to ensure clean, debris-free air reaches the engine. However, oil can clog these filters, stifling the performance of your lawn mower.

• The Engine’s Silent Cry for Help

As mechanics, we often don’t just address the damages but interpret the hidden signals these machines give us. The engine of a lawn mower is its heart, and an ignored oil leakage might slowly but surely lead to internal engine problems.

These internal issues can start subtly but soon escalate, multiplying your repair costs exponentially. Put, an oil leakage is your engine’s plaintive cry for help. Addressing it promptly saves you further inconvenience.

• Creating Visual Disappointments on Lawns

As someone who takes pride in my landscaping results, I’m always looking for anything that affects the quality of my work. Oil leakage is a culprit that creates underwhelming lawns by causing yellowed patches.

These uneven, discolored patches could tarnish your bright green carpet of grass. Ardent landscapers would agree that these odd patches mar a pristinely painted picture of the garden, courtesy of oil leaks.

• Unseen Dangers: Emissions and Environmental Hazards

One less recognized threat of oil leakage from the lawn mower exhaust is the production of white or bluish smoke. This smoke is not a harmless by-product; it poses significant risks to the user and the environment.

While harmful to take in, the damage to the environment is genuinely unsettling. Harmful emissions like these contribute to overall air pollution, which is already at critical levels. Our planet deserves better, making it all the more crucial to fix these issues promptly.

• Fire Hazard: Igniting More Than Just Your Grass

An often-overlooked threat posed by oil leakage is the risk of fire. The leaking oil from your lawn mower is a flammable liquid, and when it drips onto the floor, it creates a potential fire hazard. A simple spark, sometimes even static electricity, can set this oil ablaze.

A fire not only damages your precious property but also runs the risk of causing personal injuries. Averting such accidents is as simple as promptly dealing with oil leaks in your mower.

Finally, I recommend the Consumer Product Safety Commission’s website if you still need more information about lawnmower oil leaks or other potential problems.

It offers information on maintaining your gardening equipment and ensuring safety. Maintaining our equipment is not just about efficiency; it’s also about safeguarding our well-being and our environment.

• Engine Leak Fixes

When you notice a leak from your engine, it’s cause for concern. However, it can often be rectified with simple steps. I suggest starting by tightening the bolts and screws. Loose engine components are a common reason for oil leaks, and a quick fix can save you unnecessary repair expenses.

• The Carburetor and Fuel Line

At times, unresolved issues might be linked to the carburetor or the fuel line. If this is the case, they may need to be replaced. Faulty carburetors can lead to fuel leakage, while problems in the fuel line can disrupt the fuel supply. However, correctly adjusting the carburetor can also prevent possible oil leaks.

• The Dangers of Tipping

Tipping the mower is a standard part of the maintenance practice. When done improperly, it can cause the oil to leak, especially if the blade hits complex objects. Strict adherence to the machine’s guidelines can safeguard against such damages.

• Handling Cracked Engine Blocks

Cracked engine blocks are a prevalent cause of oil leakage. They can compromise the engine’s integrity and functionality. Extensive repairs or even replacement might be necessary to fix this.

• Mind that Crankcase!

Overfilling the crankcase can be linked to oil leaks. When there’s too much oil, it pressures the seals and gaskets to release some, resulting in leaks. Keeping the engine oil on the correct level is crucial to avoid this.

• Valve Care

Worn valves can result in excessive oil coming out of the exhaust. This situation may be beyond the average user’s skill set. I highly recommend seeking a mechanic’s assistance for this.

• Air Filter Maintenance

A dirty air filter can cause serious problems. It can let dirt and contaminants mix with the oil, leading to leaks. Maintaining a clean or replaced air filter constitutes primary mower care.

• Dealing with Damaged Piston Rings and Worn Gaskets

Damaged piston rings and worn gaskets or seals on the engine can lead to constant oil leakage. They require attention and possible professional servicing.

• Important Routine Checks

It’s advantageous to check and clean or replace the air filter regularly. Routine checks for gasket and muffler conditions are equally important. If these parts are deteriorated, their replacement becomes necessary to prevent significant damage.

• Excess Oil Dangers

Unknowingly, we may harm when trying to ensure engine efficiency. Too much oil can lead to decreased engine performance and cause environmental harm. It’s vital to use engine oil responsibly and adequately.

You can find more information on maintaining lawn mowers at this University of Florida’s EDIS site: Maintaining your Lawn Mower.

In conclusion, thoroughly examining and consistently maintaining all mower parts are essential for optimal operation and preservation. Proper care prevents unnecessary engine damage, saving time and resources in the long run.

Understanding the Causes of Oil Leaks from Exhaust

Oil leaks in the exhaust often trace back to a dirty or clogged air filter. The air filter’s primary duty is to keep the motor clean, but the oil may escape through the exhaust when it gets dirty or clogged. Hence, keeping the air filter clean is paramount. Regular checks are crucial to prevention.

Similarly, a loose or damaged spark plug may be responsible. The spark plug establishes an ignition source for the engine. If it loosens or sustains damage, oil may leak into the exhaust. Timely checks and maintenance are necessary to avoid this problem.

Likewise, a slipping belt on the motor housing could be responsible for the oil leak. The oil leak may also come from the engine. Loose or worn-out gaskets in the oil pan or valve covers could cause this.

Moreover, worn bearings or faulty oil filters can be potential reasons. Naval Postgraduate School has comprehensive details on maintaining these mechanical parts.

• Troubleshooting Tips for Lawn Mowers

Briggs and Stratton lawnmowers are a popular choice, known for their durability. However, they aren’t immune to problems. If your mower is leaking oil, certain checks will help diagnose the problem.

Start by checking the spark plug for any oil leaks. Follow this by inspecting for air leaks in the fuel system. An air leak can easily cause the mower to consume a lot of oil.

Furthermore, troubles with the ignition switch or starter solenoid can also result in oil leaks. Troubleshooting these components often results in identifying the root cause of the problem.

• Understanding the Role of Piston Rings in Oil Leaks

A common cause of a lawn mower smoking and leaking oil from the exhaust is worn out or damaged piston rings. The piston rings seal the area between the piston and the cylinder to prevent oil from leaking into the combusting chamber.

However, over time, these rings can wear out or get damaged. Consequently, oil leaks into the combustion chamber, resulting in too much smoke from the mower’s exhaust.

• Quick Checks to Ensure Your Piston Rings Aren’t Damaged

To determine if a worn-out piston ring is the culprit, remove the spark plug wires and examine the bottom side of the engine where it connects to the crankcase cover. You’re looking for oily spots, a sign that the piston rings are worn out. Regular checks are recommended to avoid large-scale damage.

• Addressing Oil Leaks promptly is Crucial: Here’s Why

Managing oil leaks isn’t just about maintaining the mower. It’s also about personal health and environmental safety. Breathing in oil fumes for long periods can be hazardous to health. Not to mention, oil leaks could contaminate nearby water bodies and harm aquatic life.

Therefore, addressing oil leaks promptly is crucial. If the leakage is extensive and beyond basic troubleshooting, seek professional assistance. Remember, timely intervention can prevent a minor problem from becoming big.

In conclusion, understanding the root cause of the oil leakage from a lawn mower exhaust is essential. From dirty air filters to worn-out piston rings, multiple potential reasons could trigger oil leaks. Regular checks and maintenance can go a long way in ensuring the durability and efficiency of your lawn mower.

If DIY troubleshooting seems tricky, consider expert help. Professionals have the requisite expertise to diagnose and fix any issues. Expert intervention can save you time and additional resource expenditure in the long run.

Effect of Oil Leakage on Lawnmower Engines

Oil leakage drastically impacts the performance and longevity of your lawnmower’s engine. Leaking oil causes the engine to work harder, significantly shortening its lifespan. Furthermore, this can potentially lead to dangerous conditions if not promptly addressed.

• Ensuring Regular Maintenance and Proper Care

To prevent oil leakage issues, you must undertake regular maintenance and proper care of your lawnmower. This includes timely oil replacements, regular check-ups, and immediate repair of worn parts.

These steps effectively ensure the continued optimal performance of the mower and prolong its useful life.

• Environmental and Aesthetic Damage

Besides affecting the lawnmower, oil leakage can cause environmental and aesthetic damage to your yard. The oil can seep into the ground, contaminating the soil and groundwater. It also disfigures the beauty of your yard by creating unsightly patches and stains.

Over the years, I’ve learned to spot signs of oil leakage, such as visible oil dripping from the exhaust, excessive smoke, or a noticeable decrease in engine performance.

• Internal Engine Problems and Oil Leakage

Technical defects and internal engine problems can cause oil to be expelled through the lawnmower’s exhaust. Prompt identification and rectification of these issues can prevent further damage and maintain the engine’s overall performance.

• Identifying the Cause of Leakage

Before fixing the oil leakage, its specific cause must be identified appropriately. There could be several reasons, like worn seals, a stuck carburetor, or even overfilled crankcases leading to leakage. By determining the exact cause, you can adopt an effective solution.

• Dangers of White Smoke from Oil Leakage

White smoke emitted from the engine due to oil leakage is hazardous. This indicates a severe underlying issue with your lawnmower’s engine and can cause respiratory problems if inhaled.

• Replacing Worn Valves

Worn valves often cause oil to leak. Regular inspection and timely replacement of these valves is critical to prevent further oil leakage and damage to the engine.

• Effects of Oil Leakage on Grass

Oil leaks can have harmful consequences on the grass. It can cause patches of grass to die off, ruining your yard’s overall aesthetic.

• Safety in Repair

When repairing the lawnmower, safety precautions must be stringently followed. Always disconnect the mower’s ignition lead to prevent accidental start-up, and if you’re not confident about doing it yourself, seek professional help.

• Preventing Oil Leakage

You can prevent oil leaks through regular, proper maintenance of the engine. Ensuring the right oil level and cleaning the crankcase vent parts are simple steps that can help maintain the health of the mower.

• Overfilled Crankcase and Oil Leakage

An overfilled crankcase or an improperly connected vent tube can cause oil leakage. By keeping an eye on these aspects, you can prevent such situations.

• Proper Maintenance of Crankcase

Regularly checking the oil level and cleaning the crankcase vent are essential preventive measures against oil leaks. Careful maintenance also increases the parts’ lifespan and the engine’s overall performance.

• Other Causes of Oil Leakage

Apart from the above points, other causes of oil leakage may exist. These may involve worn valve seals or seats, a stuck carburetor float, or even turning the mower on its side.

• Repair or Replacement

At times, the damage caused by oil leakage can be severe, leading to the need for either repair or replacement. This decision ultimately depends on factors such as the extent of the damage, repair cost, and lawnmower’s age.

• Reader Suggestions

Some readers have found it helpful to regularly check the oil level and consistency and smell it for signs of gasoline contamination to prevent oil leakage. These simple observations can provide early warnings to prevent grave damage.

• Professional Help

Despite all the preventive measures and tips, the wisest action is to seek professional help if the issue persists. Small engine shops have experienced technicians and proper equipment to handle these situations.

Like any appliance, lawnmowers require regular care and maintenance to operate efficiently.

The U.S. Environmental Protection Agency provides useful guidelines on properly disposing of oil and other hazardous waste, which can also help maintain a clean and healthy backyard. Your lawnmower can serve you efficiently for many years with proper care and attention.

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  1. Derek Moore says:

    How do I know if my lawnmower’s oil is bad and causing it to leak from the exhaust?

    • Allard Vdhooft says:

      Thanks for reaching out, Derek! If you notice oil in the lawnmower’s exhaust, it could be due to various issues like a clogged air filter or faulty carburetor. Regular maintenance is key.