Lawn Mower Leaking Oil From Air Filter

Lawn Mower Leaking Oil From Air Filter Image

Is your lawn mower leaving unsightly oil stains on your once-pristine lawn? The sight of oil pooling around the air filter can concern any lawn enthusiast. 

A leaking oil issue creates a mess and could signal underlying problems in your mower’s engine. Understanding the causes behind this issue is crucial for effective troubleshooting and maintenance. 

In this article, we’ll delve into the common reasons behind a ‘lawn mower leaking oil from air filter’ and practical steps to diagnose, address, and prevent this issue.

Discover how to keep your lawn mower running smoothly and your lawn looking its best.

Signs of Oil in the Air Filter of a Lawn Mower

White or blue smoke from the exhaust

White or blue smoke emanating from your lawn mower’s exhaust occurs when oil seeps into the cylinder and gets burned along with the fuel. 

The resulting smoke is thicker and more prominent than the usual exhaust fumes, often accompanied by a distinct burnt oil smell. This issue demands prompt attention to prevent further engine damage.

Oil dripping on the ground

If you notice oil accumulating on the ground beneath your lawn mower, it’s a strong indicator that oil is leaking from the engine. This leakage could be due to damaged seals, gaskets, or an overfilled crankcase. 

Addressing the source of the leak to prevent a messy yard but also to safeguard the mower’s overall performance and longevity.

A burning smell

A noticeable burning odor, particularly when the lawn mower is in use, often points to oil coming into contact with hot engine parts. 

This can happen if the oil leaks onto surfaces where it shouldn’t, causing it to heat up and emitting a distinct burnt smell. Ignoring this sign can lead to potential engine overheating and increased friction, causing extensive damage over time.

Strange noises in the engine

Unusual noises, such as knocking, rattling, or grinding, coming from the engine can indicate oil-related problems. When oil leaks into places it shouldn’t be, it can disrupt the proper lubrication of crucial components, increasing friction and wear. 

These sounds indicate that internal engine parts are not functioning as they should, demanding thorough inspection and repair.

Difficulty Starting the Engine

Struggling to start the lawn mower’s engine could result from oil infiltration affecting the spark plug. Oil-soaked spark plugs have difficulty generating the necessary spark to ignite the fuel mixture, leading to extended cranking times or failure to start. 

Why Is My Lawn Mower Leaking Oil From the Air Filter

 Lawn mowers leak oil from the air filter due to worn-out gaskets, damaged seals, or overfilled oil levels. These issues can allow oil to escape and access the air filter, leading to problems like white/blue smoke, decreased engine performance, and difficulty starting. Regular maintenance and proper oil level checks can help prevent such leaks. 

Causes of Oil in the lawn mower’s air filter

An oil leak occurs when there are underlying issues within the engine. These causes can lead to oil finding its way into the air filter housing, potentially affecting engine performance, combustion efficiency, and overall functionality.

They include: 

1. Incorrect procedures

Improper oil change or maintenance procedures can lead to oil entering the lawn mower’s air filter. If oil is not poured correctly into the designated compartment or if the mower is tilted excessively during maintenance, oil can escape its intended path and seep into the air filter chamber.

This can disrupt the air-to-fuel ratio, decrease combustion efficiency, and result in smoke, reduced engine performance, and potential starting difficulties.

Adhering to manufacturer-recommended oil changes and maintenance procedures is essential to prevent this issue and ensure the proper functioning of the mower’s engine and filtration system.

2. Overfilled crankcase

An overfilled crankcase can leak into the air filter by adding too much oil during the oil change. Excess oil creates pressure within the engine, pushing oil through various pathways and potentially into the air filter compartment. 

This can result in oil-soaked air filters, decreased engine efficiency, and even white or blue smoke in the exhaust. Regularly check the oil level and adhere to the manufacturer’s recommended oil capacity to maintain proper lubrication, prevent pressure-related leaks, and ensure the optimal performance of the lawn mower’s engine and filtration system.

3. Oversoaked air filter

An air filter that has been oversoaked with oil can contribute to oil leakage into the air filter housing. When an air filter is saturated with excess oil during maintenance, it becomes less effective at filtering air properly. 

This can allow oil particles to pass through the filter and enter the engine, affecting combustion and engine performance. Regularly inspecting and maintaining the air filter, ensuring it’s properly installed and not oversaturated with oil, is crucial to prevent oil contamination issues and maintain the efficiency of the mower’s filtration system.

4. Internal problems

Underlying internal issues within the engine, such as worn piston rings or faulty seals, can contribute to oil entering the air filter. When engine components are responsible for containing and directing oil malfunction, oil can bypass its intended pathways. 

This oil can then find its way into the air filter chamber, impacting filtration efficiency and potentially causing performance problems. 

Should you notice such a sign, address these problems promptly to ensure optimal engine function and maintain the integrity of the lawn mower’s filtration and combustion systems.

5. Tipped lawn mower

Tipping a lawnmower excessively or at incorrect angles can lead to oil spillage into the air filter and air intake. When the mower is tilted, especially with the air filter positioned in a way that’s vulnerable to oil flow, oil can escape from its designated compartments and flow into the air filter housing.

This can result in contaminated air filters, disrupted engine combustion, and potential performance issues. 

Avoid abrupt or improper tilting of the lawnmower during maintenance to prevent oil leakage into the air filter and maintain the proper functioning of the engine and filtration system.

6. Worn-out gasket

A deteriorated or worn-out gasket, such as the one sealing the engine components, can lead to oil leaking into the air filter area. Gaskets are useful when creating a tight seal between engine parts, preventing oil from escaping its designated pathways. 

Gaps can develop when gaskets degrade due to age, usage, or inadequate maintenance, allowing oil to seep into unintended areas. This can result in contaminated air filters, decreased engine performance, and potential oil leakage. 

7. A defective valve cover

A valve cover with defects, such as a damaged gasket or seal, can contribute to oil entering the air filter area. The valve cover is critical in sealing the engine’s top and preventing oil leaks. When the gasket or seal is compromised, oil can escape its designated compartments and find its way into the air filter housing. 

This may lead to oil-soaked air filters, potential engine performance issues, and reduced efficiency. You must ensure the integrity of the valve cover components to maintain proper engine lubrication and prevent oil-related complications.

8. Clogged air filter

A clogged air filter can be a culprit behind oil entering the air filter housing. When the air filter becomes blocked due to dirt, debris, or improper maintenance, it can disrupt the engine’s airflow and pressure balance. 

This imbalance creates excess pressure within the engine, pushing oil out of its intended pathways and into the air filter compartment. Resulting in oil-contaminated air filters, reduced combustion efficiency, and potential engine performance issues.

How to Fix a Lawn Mower Air Filter Soaked in Oil

We suggest you try the following mechanisms to fix the 9 causes of Oil in the lawn mower’s air filter: 

i. Always follow the manufacturer’s recommended procedures.

When dealing with an oil-soaked air filter, it’s essential to adhere to the manufacturer’s recommended procedures for maintenance and cleaning. Consult the owner’s manual for specific guidance on how to address the issue. 

This may involve removing the air filter, cleaning it properly, and allowing it to dry before reinstallation. Sticking to the manufacturer’s guidelines ensures that you tackle the problem effectively and maintain the integrity of the filtration system.

ii. Carefully measure and pour the recommended amount of oil

To prevent overfilling the crankcase and subsequent oil leakage into the air filter, measure and pour the exact amount of oil recommended by the manufacturer. Use the dipstick to verify the oil level after filling. 

Proper oil levels will prevent excess pressure buildup, reducing the risk of oil escaping into unintended areas. As such, you maintain engine lubrication while safeguarding the air filter and overall mower performance.

iii. Avoid oversaturating the air filter with oil

When addressing an oil-soaked air filter, it’s crucial to apply oil carefully and moderately during maintenance. Applying too much oil lead to oversaturation, where the filter becomes excessively soaked. 

Yet, an oversaturated air filter can’t effectively filter air, and excess oil can find its way into the engine, causing combustion issues and decreased performance. Remove the air filter, gently clean it, and apply a thin, even layer of oil per the manufacturer’s guidelines.

iv. Address internal engine issues by consulting a professional mechanic

If your lawn mower’s air filter is soaked in oil due to internal engine problems, such as worn piston rings, faulty seals, or an oil pump, it’s best to seek expertise.  

A professional mechanic or small engine specialist can diagnose the underlying issues and perform the necessary repairs to restore the engine’s integrity. Fixing complex internal problems without proper knowledge can lead to further damage. 

By consulting a mechanic, you ensure that the root cause of the oil leakage is properly identified and resolved, preserving the functionality and longevity of your lawn mower.

v. See the angle of your lawnmower

Ensure the air filter side is positioned upwards to prevent oil from spilling into the air filter chamber when tilting your lawnmower. This positioning prevents oil from flowing into the filter compartment, reducing the risk of contamination. 

Then, allow the lawn mower to rest upright for a few minutes before restarting. This allows excess oil to settle back into the crankcase, minimizing the chances of oil leakage into the air filter. 

vi. Inspect and replace worn-out gaskets as needed

If your lawnmower’s air filter is soaked in oil due to a worn-out gasket, such as a damaged valve cover seal, you need a timely replacement. 

Inspect gaskets for signs of deterioration, such as cracks or gaps. If found, replace the gasket promptly to reestablish a proper seal and prevent oil leakage. 

You can seek professional assistance for accurate gasket replacement. By addressing worn-out gaskets, you ensure that oil remains within its designated pathways, preventing contamination and safeguarding the air filter. 

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vii. Replace a defective valve cover gasket or seal with a new one

A damaged gasket or seal can allow oil to escape its designated pathways and enter the air filter compartment, leading to contamination and potential engine problems.

You’ll need to replace the blown head gasket or seal with a new one. Begin by locating the valve cover, which is responsible for sealing the top of the engine. Carefully remove the old gasket or seal, leaving no debris or fragments behind.

Clean the mating surfaces thoroughly to ensure a proper seal with the new gasket or seal.

viii. Regularly inspect the air filter and clean or replace it as necessary

Establish a routine of inspecting the air filter during maintenance. Clean or replace the air filter as recommended by the manufacturer.

A clean filter ensures proper airflow, reducing the risk of pressure-induced oil leakage. Regular maintenance practices contribute to efficient engine performance and prolong the life of your lawn mower.

Types of Air Filters

There are two main types of air filters: paper air filters and foam air filters. 

Paper Air Filter

Paper air filters are commonly used in various engines, including lawnmowers. They consist of pleated paper material that efficiently traps dust, debris, and contaminants from entering the engine. 

While they are effective in filtration, they may require more frequent replacements due to their disposable nature. They are cost-effective and suitable for general applications, offering moderate filtration efficiency.

Foam Air Filter

Foam air filters are made from porous foam material. They provide excellent filtration by capturing particles before they reach the engine. Foam filter can be washed and reused after cleaning, making it more environmentally friendly and cost-effective over time. 

However, their filtration efficiency may be slightly lower compared to paper filters. They are suitable for dusty environments and can handle moderate debris levels.

Tips When Replacing an Air Filter to Prevent Oil Leaks

  • Before installing the new air filter, carefully examine the gaskets and seals around the air filter compartment. Ensure they are in good condition and properly seated.
  • Adhere to the manufacturer’s instructions for replacing the air filter. This includes proper orientation and positioning of the filter. Incorrect installation can disrupt the sealing and potentially lead to oil leakage.
  • If your air filter requires oiling, apply a thin and even layer as instructed. Over-oiling can lead to excess oil seeping into the engine, potentially causing leaks and affecting combustion efficiency.
  • Ensure the air filter housing is securely closed and fastened after installing the new filter. Loose housing can allow debris and contaminants to enter the engine, leading to oil contamination.
  • Regularly inspect and clean or replace the air filter according to the manufacturer’s recommendations. Keeping the filter clean and in good condition reduces the likelihood of oil leaks caused by clogs or improper filtration.
  • When working on the lawnmower, ensure it is on a level surface. Tilting the mower excessively during air filter replacement can lead to oil spillage into unintended areas.
  • After replacing the air filter, check the oil levels and ensure they are within the recommended range. Overfilled crankcases can increase pressure, potentially causing engine oil to escape into the air filter chamber.

Why is Oil Coming Out of the Air Filter of These Lawn Mowers

Oil leakage from the carburetor and air filter in various lawn mower brands can stem from specific issues. Understanding these causes and implementing proper solutions is essential for maintaining engine performance and preventing further complications. 

Briggs and Stratton lawn mower oil leaking from air filter

Oil leakage from the air filter in Briggs and Stratton lawn mowers often indicates a malfunctioning breather system. The breather system regulates pressure within the engine; if it fails, excessive pressure can force oil into the air filter. 

To fix this, inspect and replace the breather components as needed. Regular maintenance of the breather system ensures proper pressure control, preventing oil leaks into the air filter.

Toro lawn mower leaking oil from air filter

Toro lawn mowers may experience oil leakage due to a damaged or worn-out gasket on the valve cover. A faulty gasket allows oil to escape and reach the air filter compartment. 

Replacing the gasket with a new one is essential to restore proper sealing and prevent oil leaks. Regularly inspecting and maintaining gaskets ensures a tight seal, keeping oil within its designated pathways.

Craftsman lawn mower leaking oil from air filter

In Craftsman lawn mowers, oil leaking from the air filter can result from an overfilled crankcase. Adding excessive oil during maintenance increases pressure within the engine, causing oil to find its way into the air filter area. 

To resolve this, carefully measure and pour the recommended amount of oil, avoiding overfilling. Checking and maintaining proper oil levels prevent pressure-induced leaks and maintain engine performance.

 Husqvarna riding mower leaking oil

Oil leakage in Husqvarna riding mowers, as indicated by Husqvarna ratings, could stem from a worn-out or damaged piston ring. A compromised piston ring allows oil to seep into the combustion chamber, leading to oil burning and residue entering the air filter. Replacing the piston ring resolves this issue. 

Regular inspection and maintenance of engine components, particularly piston rings, are crucial to preventing oil leaks and ensuring efficient engine operation.


Can Oil Leak Damage Your Engine?

Yes, oil leaks can lead to engine damage. Leaked oil can compromise lubrication, causing increased friction and heat. This can lead to premature wear on vital engine components, such as pistons and bearings. Oil leakage can also contaminate other engine systems, affecting overall performance. 

Can Hitting Something Cause An Oil Leak?

Yes, hitting an object can damage the mower’s undercarriage or components, leading to oil leaks. The impact can rupture oil pans, crack gaskets, or damage drain plugs. These damages can cause oil to escape, resulting in insufficient lubrication and potential engine issues. Regularly inspect your mower after hitting obstacles and address any visible damage to prevent oil leakage.

Why is my push mower leaking oil from air filter?

A push mower leaking oil from the air filter could indicate overfilling of the oil reservoir. Excess oil increases pressure and forces oil into unintended areas like the air filter. Drain the excess oil to the proper level and avoid overfilling in the future. Regular oil level checks during maintenance prevent pressure-induced leaks and maintain engine efficiency.

Can Using the Wrong Type of Oil Cause an Air Filter Oil Leak?

Yes, using an inappropriate oil type can contribute to air filter oil leaks. Oil that’s too thin or too thick for your mower’s specifications can affect proper lubrication and circulation. This can lead to excessive pressure, pushing oil into the air filter. Stick to the oil grade the manufacturer recommends to prevent compatibility issues in the oil filter and maintain engine integrity.


 Generally, a lawn mower leaking oil from the air filter is a concerning issue with multiple underlying causes. Whether it’s due to incorrect procedures, worn-out gaskets, internal engine problems, or other factors, timely and accurate diagnosis is crucial.

Maintenance, adherence to manufacturer’s guidelines, and proper oil level checks are essential to prevent oil leaks. 

Most importantly, addressing these issues promptly preserves your mower’s longevity and ensures efficient engine performance, clean air filtration, and a healthier lawn.  By staying vigilant and proactive, you can enjoy a well-maintained mower and a beautifully