There are several issues that could be making your lawnmower burn oil. This is usually pretty simple to troubleshoot when you know what you are looking for.
Common reasons a lawnmower will burn oil include:
- Too much oil in the engine’s crankcase
- Using the wrong oil grade
- Not enough oil
- A blown head gasket
- An oil leak
- Improper storage
Let’s take a look at these common problems one by one and what needs to be done to fix them.
Too Much Oil in the Engine’s Crankcase
Most lawnmower engines contain a solenoid that monitors the flow of gas into the engine. The float in the carburetor connects to a solenoid that regulates the fuel flow into the engine. If the carburetor float that connects to the solenoid gets stuck, it will prevent the fuel shut off (source).
This will allow too much gas into the engine and thin the oil. The thin oil burns more quickly, and this will trigger the engine to make that white smoke.
If your lawnmower is burning oil because you have overfilled the crank case, you may need to repair the carburetor. You should certainly drain the oil and fill the crankcase with new oil, paying attention to the manufacturer’s recommendation for the proper amount and type needed.
Using the Wrong Oil Grade in Your Lawnmower Can Cause it to Burn Oil
The wrong grade of oil could cause problems with your lawnmower and may be a cause of it burning oil as well. Not all lawnmowers use the same type of oil. You may think using a different grade of oil will increase efficiency, but you may be wrong.
Using the wrong viscosity of oil may make your lawnmower run more slowly. The wrong weight of oil may cause damage to the engine.
If your engine is designed to use a heavier oil, a lighter weight oil will burn more quickly.
To really understand the impact of using the wrong grade of oil, watch this in-depth video from YouTube:
Check your owner’s manual for the best type of oil recommended for your lawnmower.
Not Enough Oil Can Actually Be The Cause Of Burning Oil
As your lawnmower engine uses more oil, the temperatures rise inside the crankcase. This results in more oil being burned. As the level of oil in the crankcase decreases, the friction in the engine increases. The engine heats up more and as a result, burns more oil.
To fix this situation, make sure to monitor the oil levels in your lawnmower’s engine as described in your owner’s manual.
If you suspect your oil level may be running low, add more to bring it to the correct level. This will prevent wear and tear on your engine and avoid having to make future repairs.
A Blown Head Gasket Will Cause Your Lawnmower to Burn Oil
A head gasket on a gas engine is located between the engine block and the cylinder head. It is vital to ensure that the internal combustion process is running properly and efficiently by sealing off the engine block. A head gasket also serves to keep the oil and coolant from combining in the engine.
If you have a blown head gasket, your lawnmower will suddenly lose power. Look for oil leaking from around there, the gasket, and the engine block meet.
A blown head gasket can cause more damage to your lawnmower engine than just leaking oil.
- You will notice smoke coming from your engine.
- Your lawnmower will run rougher than normal.
- You will notice your engine tends to overheat.
- Your lawnmower engine will burn oil.
If you suspect you have a blown head gasket, you may find it is easier and less costly to have the head gasket replaced rather than attempting to repair it.
While the process to repair a blown head gasket is not difficult in theory, you will need to pull out several parts and put them back properly to be a successful repair.
This YouTube video gives a great visual representation of a blown head gasket.
Leaking Oil Can Cause Your Lawnmower to Burn Oil
If oil is leaking somewhere in or around your lawnmower engine, the engine’s heat will cause the leaked oil to burn. This may make the leaks worse as damaged seals and gaskets are damaged even more. You may notice gray or white smoke emanating from your engine if your lawnmower is leaking oil.
One of the more important tasks to avoid having to fix your lawnmower in the future is regular engine maintenance.
- Make sure you drain and replace the old oil with new after about every 25 hours of use.
- Regularly check your piston rings for wear and tear. Oil can easily leak through even the smallest gaps and cause even more damage to your lawnmower engine.
- At the end of the season, don’t put your lawnmower away with oil and gas still in it. The old oil can cause the gaskets and seals to deteriorate and rot away, resulting in an engine repair bill the next time you try to start up your lawnmower. Not a nice surprise come the next spring!
Storing Lawnmower on Its Side May Result in Your Lawnmower Burning Oil
Garage space is sometimes at a premium, and it is not all that unusual for owners to store the push lawnmowers on their sides when they are not being used. Some people also turn the lawnmower on its side when they change the oil or perform other maintenance.
If you are one of these owners that tilt their lawnmower when it is put away or make repairs, there are some steps you can do to fix this situation and avoid having a problem in the future.
- Drain the oil and gas before you put your lawnmower away. As mentioned above, letting the parts of the lawnmower sit in oil and gas for extended periods of time could cause great damage to your engine.
- Check the position of your sparkplugs when making repairs or doing maintenance. They should be kept facing upwards to avoid leaks from the crankcase.
How Can You Tell If Your Lawnmower Engine is Burning Oil?
There are many reasons your lawnmower may not be working like it did when it was new. Burning oil could be the reason behind its poor functioning.
There are more than just these six causes for your lawnmower burning oil. And there are more than just a few ways to fix them. The best way to determine if your lawnmower is burning oil and how to fix it, is to study the lawnmower itself.
A little white smoke may be normal when you first start up your lawnmower. A lot of white smoke may indicate a bigger issue, such as a blown head gasket.
The same is true if you see black smoke. A little may not be cause for worry, but you still want to investigate the reason behind it. It could be as simple as a dirty air filter or a more serious issue with a fuel regulator.
A Sluggish Engine Could Indicate Oil Leak
You may find your lawnmower engine is not performing as it used to. It may be sluggish or run in spurts. That could mean leaking oil from damaged piston rings or seals.
If you suspect your lawnmower is burning oil, you need to check the engine and all its components as soon as possible to avoid more damage and possibly big repair bills.
If you are just sick and tired of fighting with that gas engine, you may also want to read Are Electric Lawn Mowers Worth It? Know These 4 Use Cases.