Why Is Oil Coming Out Of My Lawn Mower Exhaust
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Why Is Oil Coming Out Of My Lawn Mower Exhaust?


Is your lawnmower leaking oil from its exhaust? Don’t worry; it sometimes happens if you are using petrol propelled machine. But, try to fix this problem as soon as possible.

There are several reasons why your lawn machine is dripping oil. An overfilled crankcase, impaired piston ring, or fluid shifting when the tool tilts on its sides are some of the common reasons. You need to identify the source of oil escape, and then you can quickly fix it.

In this post, we will discuss all the positional reasons why oil coming out of lawn mower exhaust. You can find the cause and then follow the given solution to bring back the mower to normal.

Why Is My Lawn Mower Leaking Oil From Exhaust?


When you power on a lawnmower, it starts by heating four components, including cylinders, pistons, exhaust manifold and exhaust pipe. Then, oxygen and fuel flow inside the piston that compresses explodes the gas and pushes it to come out of the exhaust.

Oil is responsible for lubricating all the movable parts. If any of the internal components are damaged or end of life, then you might notice oil leaking from the muffler on lawn mower.

Top Reasons Why Lawn Mower Spitting Oil Out Exhaust


Lawn Mower Spitting Oil Out Exhaust

Damaged Piston Ring: The pistons are one of the essential parts of your lawn machine. It distributes gasoline and oxygen to combust so that the tool can run without any problem. As the pistons are constantly on the move, they need oil for lubrication.

A rubber made component that seals oil leakage is called a piston ring. If it’s damaged or worn out, then the liquid will start dripping. This ring can last for many years but can stop containing the oil because of non-maintenance and some other factors. Once the oil slips from the piston, it will gel with gasoline and start oozing from the exhaust.

Solution: Replace the piston ring

Overfilled Crankcase: The crankcase holds a crankshaft, which is a crucial part of your mower’ engine. When you download oil into the mower, most of it goes into shaft lubrication. However, you don’t have to fill too much oil. If you overfill the tank, the extra oil will flow towards the cylinder, and you will notice fuel coming out of exhaust lawnmower.

Solution: Clean the carburetor and make sure you don overfill next time onwards

Filthy air filter: It is not common, but an oversoaked filter is one reason why oil coming out of the exhaust lawn mower. An air filter is a passage for oxygen to flow inside the engine and complete the combustion. What if the filter is very dusted? Lack of airflow means that the amount of gas will be higher. In such a situation, the extra liquid will flow towards the exhaust via the muffler. So, you might think that the mower is leaking oil, but it’s gasoline.

Solution: Replace the air filter

Worn or end of life valves: A mower’s engine comprises two valves, wherein each one of them fulfills the intake and exhaust process. After several years of regular usage, these valves can start malfunctioning. It means that the cylinders will not be entirely sealed when the mower is under operation. Result – oil makes its way to the exhaust.

Solution: Repair the valves if possible or replace them

Tipped lawn mower: If you are tipping a walk-behind or self-propelled mower on its sides, then there are chances the oil will leak towards the exhaust. It happens when you lean the mower inappropriately and create a passage for the oil to enter the carburetor or the muffler.

Solution: While beveling the mower, you need to ensure that its carburetor remains on the high side.

Blown head gaskets: Head gaskets block the heads of the mower’s engine. In other words, it seals the passage between heads and blocks. So, when the gaskets are end of life or worn out, liquid flows to the exhaust.

Solution: If the mower can run for more than 15 minutes without overheating, then you can try to repair the gasket seal maker by Visbella. But, you need to replace the gaskets if the engine overheats within 15 minutes of running.

Cracked Engine Block: The engine block contains all the internal parts and also facilitates a passage for oil so that it can reach all the components. If this block has cracks, then the fluid will escape, and you will notice fuel coming out of exhaust lawnmower. Also, the mower will not perform according to your expectations; it will overheat and make extra noises when operational.

Solution: Contact a mower expert for repair or replacement

Tips To Avoid Oil Leaking From Muffler On Lawn Mower


  • Perform regular maintenance to keep the mower in top condition and prevent any oil leaks.
  • Do not overfill the oil tank.
  • Keep the carburettor upwards when you are cleaning the motor. Do not tilt it more than 15 degrees. Otherwise, the oil will distribute, and finally, it will start leaking from the exhaust.
  • Inspect the air and fuel filter periodically. Spray carburettor cleaner to degrease it and to ensure that the leaked liquid cannot allure extra dirt.
  • If you are a beginner and cannot fix any of the issues discussed above, then it’s recommended that you consult a professional.

Dangers Of Oil Coming Out Of Exhaust Lawn Mower


  • White smoke: Oil reaches various internal components, burns and creates white smoke. This harmful exhaust can damage your lungs and is dangerous for the environment as well.
  • Dead grasses: Fluid dripping on the lawn grasses will kill them. Hence, your garden will appear rough and patchy.
  • Difficult starting: Excess of oil in the tank might prevent the engine’s startup.
  • Fire hazard: Fuel coming out of exhaust lawnmower is inflammable, and hence it’s a potential fire hazard.

Final talk


Now you know why the lawn mower leaking oil from the exhaust and how to fix it. So, you can quickly fix there is any leak in the mowing tool. Consult a professional if you are a beginner.

Some of the lawn owners do not care much about the mower or its maintenance. However, it’s not the proper practice. It would help if you spent some time servicing the lawn machine to keep it running for a long time.

Last Updated on May 17, 2021

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