1) Excessive oil level: If the oil level in the lawn mower is too high, it can cause oil to be drawn into the combustion chamber and burned, resulting in oil in the exhaust. Check the oil level and ensure it is at the correct level as specified in the lawn mower's user manual.
2) Worn piston rings: Piston rings are responsible for sealing the combustion chamber and preventing oil from entering it. If the piston rings are worn or damaged, they can allow oil to leak into the combustion chamber, resulting in oil in the exhaust.
3) Faulty PCV valve: The PCV (positive crankcase ventilation) valve is responsible for regulating the flow of gases from the crankcase to the intake manifold. If the PCV valve is faulty or clogged, it can cause pressure to build up in the crankcase, forcing oil into the combustion chamber and resulting in oil in the exhaust.
4) Clogged oil filter: A clogged oil filter can restrict the flow of oil to the engine, causing the oil pressure to increase. This can force oil past the piston rings and into the combustion chamber, resulting in oil in the exhaust.
5) Incorrect oil viscosity: Using an oil that is too thin or too thick for the lawn mower can cause problems. If the oil is too thin, it may not provide adequate lubrication and protection for the engine components, resulting in increased wear and tear. If the oil is too thick, it may not flow properly and can cause increased pressure in the crankcase, leading to oil in the exhaust.
6) Engine damage: In some cases, oil in the exhaust can be a sign of more severe engine damage, such as a cracked piston or damaged cylinder head. If you suspect that the engine is damaged, it is important to have it inspected and repaired by a qualified technician.
If you notice oil in the exhaust of your lawn mower, it is important to address the problem promptly to prevent further damage to the engine. Check the oil level, PCV valve, and oil filter, and ensure that you are using the correct oil viscosity as specified in the lawn mower's user manual. If the problem persists, it is recommended to have the lawn mower inspected and repaired by a qualified technician.
