What Does It Mean If A Lawn Mower Is Burning Oil?

Engine oil is an essential part of a combustion lawnmower’s operation and longevity. Each time you mow your lawn, the machine uses up a little bit of the precious liquid, which is why it needs to be changed or topped up after a while.

A mower engine that is burning oil usually means one of a few things. Excessive smoke and burning oil can be an issue caused by…

  • Aged oil
  • Inconsistent fuel levels
  • The wrong oil grade
  • Internal oil leaks
  • Low oil level
  • Blown head gasket

Sometimes a lawnmower might use up a little too much oil, a problem that reveals itself through several symptoms. What are these symptoms and, more importantly, how can the overall problem be rectified? 

Let’s take a look.


Why Would A Lawn Mower Burn Oil?

Perhaps you’ve noticed that you’ve had to refuel your lawnmower more frequently than usual. Or, even more worryingly, your lawnmower is producing increasing amounts of smoke every time you run it.

Large amounts of white smoke is a tale tale sign that your mower engine is burning oil.

A quick oil check soon reveals that your oil levels have dropped significantly…again. You check for leaks but find none.

Clearly, there is a problem somewhere that is using up your mower’s engine oil. In most cases, if you’re not dealing with a leak, there is a decent chance your lawnmower is burning excessive amounts of oil when it is in operation.

Not only is this problem harmful to your mower and its lifespan, but it is also a hole in your pocket because you will be forced to buy engine oil much more frequently than you should. Engine oil for 4-stroke lawnmowers is generally added or changed during service (typically every 25-50 hours), or at the start of a new mowing season.

So, what are the likeliest causes of this problem? 

Well, in truth this issue can be caused by one problem or a combination of things.

Aged Oil

One of these potential root issues is the use of aged fuel. Gasoline, especially, is well known for its somewhat limited shelf life. Lower octane or ethanol-blended gas is most likely to age and go bad much quicker than premium gas. Over time, the fuel undergoes a series of chemical reactions that thicken it and produce harmful byproducts like water. 

Both of these effects make it difficult for your lubricant (oil) to do its job. This forces the engine to use up more oil.

The Amount Of Fuel Can Cause A Mower To Burn Oil

Another issue that can cause the machine to burn through more oil is the amount of fuel you use. Too little, and your engine will begin to run hotter than normal. This increases its demand for oil, which also plays a role in helping the engine keep cool.

Too much fuel may flood the mower’s crankcase, which can lead to the oil becoming thinner. Oil burns much more rapidly when it gets thinned out like this. Pay attention to your lawnmower’s fill-up point to avoid overfilling it. If you do overfill the machine, try to avoid mowing on uneven ground or even tipping the mower over because you will flood the crankcase.

The Wrong Oil Grade Can Cause Burning

Sometimes the problem lies with the oil itself. Using the wrong oil grade can result in similar issues. Many lawnmower owners make the mistake of not reading their instruction manuals and, as a result, they may miss out on key information such as the recommended oil grade for the machine.

Engine oils vary in terms of lubricative qualities and viscosity. Mower manufacturers recommend the best grades for each of their machines and failure to follow these instructions will result in the machine burning through more oil.

Aged Oil Can Be Burning Oil

Aged oil is another thing to look out for. Much like fuel, oil can go bad and lose its qualities. Leaving oil in the machine for the winter is especially bad. Loss of lubricative qualities, in particular, may force the machine to use up more oil.

Internal Oil Leaks Lead To Oil Burning

While we mostly associate oil leaks with droplets of oil on the ground, you must also be aware of internal oil leaks, which can also lead to this problem. Such leaks commonly occur in the lubricating system, oil gaskets, and breather cavity. One of the tell-tale signs of an internal oil leak is excessive exhaust smoke.

What does excessive exhaust smoke tell you? Your engine is burning oil.

Low Oil

Another potential root issue is your oil level. Low oil levels create a vicious cycle within your machine. The lower the oil, the lower the engine lubrication…which increases the oil demand. This will lead to the engine burning through even more oil.

A Blown Head Gasket Can Cause Burning Oil

In some rarer cases, you could have a blown head gasket on your hands. This component is vital for sealing off the combustion chamber and preventing engine oil from mixing with coolant. If the gasket is damaged, a whole host of things can go wrong, including internal oil leaks and engine overheating.

How To Fix A Lawnmower That Burns Oil?

Now that we’ve identified some of the root issues for this situation, let’s take a look at the potential solutions.

Consistent Fuel Levels

For fuel-related problems, you want to make sure that you use the correct amounts of gas/diesel. Do not let the mower run too low but be careful not to overfill either.

Replace Or Condition Fuel

Another thing you must do is to not let fuel sit in the mower for too long. If you must put your mower into storage for the winter, make sure to drain the fuel tank and run the mower until it will no longer start. You can then fill it up when the next mowing season rolls around.

Drain Oil

The same goes for your oil. If you have to store the mower for an extended period, drain all the oil from the machine and replace it when you need to use it again.

Use The Correct Oil Grade

You should make sure you use the correct oil grade as well. Read your manual or consult the lawnmower’s manufacturer or dealer directly for the appropriate types to use. In addition, always keep an eye on your oil levels. We recommend that you check the dipstick every time you bring your mower out to cut your grass.

Oil Changes

Carry out oil changes when required. Your manual should have a detailed service schedule to guide you. Some mowers and riding tractors may have these schedules attached to them. Consult your manufacturer or browse online if you cannot find these schedules.

Routinely Inspect Mower Engines

You should also carry out general inspections on your lawnmower. This may help you identify internal oil leaks, damaged gaskets, and a host of other problems that may result in this issue. You can do this yourself or you can have a lawnmower or small engine specialist carry this out for you.

The Final Touches On Mowers Burning Oil…

If your mower is blowing out large amounts of smoke, especially after being started for more than a minute, it could be a sign that it is burning oil. Using these ideas from our experience as a starting point, you should be able to track down the cause of your problem.

Once you figure it out, the solution is usually fairly easy and inexpensive. Just get to the problem sooner than later and the issue won’t become a bigger problem affecting other functions of the mower.




Mathew Booe

Mathew has worked in landscaping professionally for over 10 years. He is a grandpa and frequently interviews other experienced landscapers and lawn care experts who are also grandpas for these articles.

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