Why Is My Lawn Mower Air Filter Soaked in Oil?

Approx Reading Time: 8 minutes

Few things are as certain as the growth of grass, and the subsequent need for a lawnmower. But, inevitably, you’ll run into issues with your mower. One of the most common is an oil-soaked air filter. Whether it be today or in the unwritten future, understanding why a lawnmower’s air filter is soaked, and how to solve it, are valuable tools in your mental toolkit.

Air filters of lawnmowers get soaked in oil naturally over time. If the air filter gets soaked in oil more frequently, the issue is most likely based on turning the mower over on the wrong side. By flipping the mower over with the air filter down, oil in the engine will leak out and drip onto the air filter, eventually soaking it and leading to poor performance. 

The main function of an air filter in a lawnmower is to act like your skin – it is essentially the first line of defense against the elements. This means dirt and grime are less likely to enter into the engine through the carburetor, thus allowing the machine to work properly. While the air filter is only one cog in the system of the lawnmower, it is imperative to protect it.

Flipping Over Your Lawnmower Will Soak its Air Filter in Oil

The most likely cause of a consistently oil-soaked air filter in a standard push lawnmower is flipping it over on the improper side in order to work on maintenance. This leads to oil spillage from the engine, which, over time, will concentrate in the air filter, congregating and eventually soaking it. Without properly filtered air, a mower will lose horsepower and strain the engine.

There are ways to maintain and repair your mower without destroying the oil filter. 

Safety Precautions Before Maintenance

Before flipping over your lawnmower over to do maintenance or check to see if an obstruction is present, be sure to remove any potentially dangerous barriers. In order to keep safe, get in the habit of following the steps listed: 

  • Allow the engine to cool off first
  • Disconnect or remove the spark plug wire so the engine does not accidentally start
  • Make sure the oil cap is on unless adding oil 
  • If possible, wear safety glasses and work gloves

Removing the potential dangers posed by the everyday lawnmower will not only keep you safe but give your lawnmower a better chance of being maintained. All in all, these safety precautions are a small sacrifice for a valuable action.

Which Side to Flip Your Mower

First thing’s first, if you are unsure which side to flip your mower on, take a look at the owner’s manual. If you lost the copy that came with the mower when you bought it, there’s likely a copy online. If you’re still unsure, don’t worry – you can just look at the placement of the spark plug(s) on your mower.

Since the air filter should be turned upward, meaning the oil is unable to spill out, the spark plug should also be facing upward towards the sky. As was mentioned earlier, be sure to check out what the manufacturer says before tipping; use this default as a back-up plan. 

If more space or freedom is needed for different cleaning or maintenance purposes, letting the lawnmower run out of gas and then manually removing any remaining oil with a siphon is a solid solution. This way, the mower can be contorted in all sorts of directions without leaking any significant amounts of oil. Again, this is only if additional freedom is needed for maintenance.

As a bottom line, when shifting the position of a lawnmower, be sure to keep the air filter facing up. Ensure the spark plug if facing the sky, as opposed to the ground. For more space, your best bet is to rid all oil and fuel from the mower, then you can flip it how you wish.

Tilting Your Lawnmower

If flipping your mower on its side is not exactly your cup of tea, or your specific lawnmower cannot be flipped on its side, there is an additional method to decide how to position your grass-eating machine. Whereas above, it was advised to turn the mower on the proper side; in this case, the alternative method is to tilt it handlebars to the ground. 

As was mentioned earlier, the most effective method of inspecting and cleaning – essentially gaining access to the underside of a lawnmower – is to flip it on its side. For an inspection with reduced freedom and visual assistance, planting the handles onto the ground and letting the bulk of the machine sit in the air will do the job. 

For simple checks and instances in which a great deal of vision is not needed, tilting rather than flipping your lawnmower is the more effective, safer option. 

As was seen with the flipping, be sure to follow safety precautions before tilting your mower.

How to Fix a Soaked Air Filter

Once the knowledge of an oil-soaked air filter is acquired, ensure that any distress or anger has not slipped into your brain; this “issue” is very easily rectified. Cleaning out or replacing the air filter and any affected spark plugs are likely the worst of any effects experienced from an oily air filter. At worst, the combustion chamber can be flooded by gas; fortunately, this too can be fixed.

Replacing an Air Filter 

Before going ahead and replacing an air filter in your mower, keep in mind that you should be putting in a new one at least every season, or after mowing for around 25 hours. Now that this is out of the way, there are two mentionable types of air filters: paper and foam. 

  • Paper Filters

When it comes to paper filters, once it has been stained or soaked in oil, there is one solution and one solution only to making your mower serviceable: replace it. Unlike its foam counterpart, paper filters cannot be cleaned and re-inserted into the mower; issues will continue if this is done. 

  • Foam Filters

Foam, the other widely used material in air filters, can, in fact, be cleaned and placed back into a functioning lawnmower. In order to adequately clean a foam air filter, wash it with hot water and soap – dish soap works the best. 

Once your filter, either paper or foam, has been replaced or cleaned, respectively, soak it with oil, then wring it out. This step will actually encourage better long-term results, as air filters are meant to be oily, just not soaked. As long as saturation does not occur, a well-fitting filter will function properly.

Fixing or Replacing a Spark Plug

Like fellow lawnmower part air filter, spark plugs can be saturated with oil, too. What is widely known as spark plug fouling in the realm of mechanics is caused by an excess of oil inside the combustion chamber. 

In order to clean a spark plug, use a wire brush or spray cleaner specifically designed for spark plugs. WD-40 and similar solutions may work in some instances, although they are not as effective as the options listed earlier. 

The unfortunate reality regarding spark plugs is that they will most likely not perform as well as prior to their flooding; for this reason, replacing them after oil floods is the best decision for engine safety and mower performance.

Fixing a Flooded Combustion Chamber

Although “flooded combustion chamber” sounds pretty bad, fortunately, it can usually be fixed by simply removing the spark plug(s). For severe cases, the best idea is to consult a professional.

How to Prevent a Soaked Air Filter

As you can see, once you have a grasp on the methods to turn or tilt your mower the right way, there is not much else to do to prevent a soaked air filter.

As a summary, remember to follow these guidelines in order to prevent future concentrations of oil in your air filter:

  • Always turn your lawnmower air filter side up
  • When additional space is not needed, tilt your mower onto its handlebars
  • When working on your mower, be sure to disconnect the spark plug cap and keep the engine turned off to avoid unintended accidents
  • When tending to a soaked air filter, replace paper ones and clean foam ones
  • Be sure to change your air filter every season or every 25 hours to maintain optimal performance

And as always, stay safe when working with your lawnmower. 

Peter Toth

Hi! I'm Peter, the owner of BackyardGadget. Working around the house has always been a big part of my life. I've created this site to share my experience, and to help people choose the right tools for the job. Thank you for stopping by!