A lawn mower is made up of so many parts, most of which we can’t see.
They all play a role in allowing us to use the mower to take care of our lawn, but some are more important than others.
So what about the humble two-dollar (give or take) air filter?
Can you run a lawn mower without an air filter?
And what will happen if you forego this inexpensive item?
We take a closer look today.
So let’s get started.
Can You Run A Lawn Mower Without An Air Filter?
You should never run your lawn mower without an air filter. The air filter prevents debris such as dirt, stones and dust from harming your mower’s engine. Just one small piece of grit that gets into your mower could wreck it completely. With air filters costing just a few dollars, running your mower without one is an expensive risk, even if you only do it once.
A Lawn Mower Air Filter Explained
Every single gas lawn mower sold on the planet has to, by law, be fitted with an air filter.
As the name suggests it filters the air to remove dirt, grass and grit from entering the engine.
Pretty much all lawn mowers are air-cooled, so the air filter ensures the air that cools the engine is clean, as well as flows uniformly to help power the engine efficiently.
Some filters are made of paper and some are made of foam, but they all perform the same job.
So how important is the air filter on a lawn mower? Very important indeed.
You can run a lawn mower without one, but what does happen if there is no air filter?
Problem #1: The Engine Will Be Damaged
We’ve already established that one of the main roles of an air filter is to prevent dirt and grit from entering the engine of a lawn mower.
So it stands to reason that, without an air filter, all kinds of debris will be free to enter the most vital component of your lawn mower and wreak havoc.
Remember that lawn mower engines already have a hard enough life as it is, as their air intakes are pretty close to the ground.
When you are mowing your lawn there will be plenty of dust, grass cuttings, grit and tiny stones swirling around and getting sucked into the combustion chamber.
Just a single small stone entering your mower’s engine could wreck it.
Running your mower without this barrier leaves it open to the risk of severe engine damage.
You might be lucky and get away with it once, twice, even a few times, but when you are mowing look at all the debris of grass, leaves, dust swirling around and think that is going straight into your engine…
It isn’t going to have a positive effect.
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Problem #2: It Will Unbalance the Air to Fuel Ratio for Your Mower
If you are running your mower without an air filter, the contaminants it ingests will not only physically damage the mower, they will make it less efficient.
Let me explain.
All of a sudden the combustion chamber will be filled with dust, grass, leaves, pollen and whatever else finds its way in. That will reduce the amount of oxygen in the chamber.
On top of that when this unwanted material is combusted in the chamber it will add to carbon build-up, which will interfere with the ignition of your mower.
From here it is a snowball effect.
With your mower unable to burn the fuel properly, flooding and fuel deposits will starve the engine of possibly both fuel and air.
With less fuel and air, more and more of these contaminants will be able to remain in the engine without being burnt off.
They will line the cylinder walls and decrease the air pressure and you will notice your mower appears to lose strength.
So when you are mowing your lawn the machine will be less efficient and have to work harder to mow it.
It will need more fuel and more strain will be placed on the engine, leading to a much earlier demise of your prized mower than you would want.
And all of this at the expense of a paper air filter that costs just a few dollars.
Doesn’t seem worth it really does it?
Problem #3: It Will Wear Out Your Mower’s Parts Much Quicker
Really this is tied in with the first two problems.
All this extra dirt and dust will clog up various parts of your mower, and mix with the oil which will wear out your cylinder walls and piston rings much more quickly.
All lawn mower manufacturers put air filters on the engines of their lawn mowers for a purpose.
That purpose is to prevent all of this damage and prolong the life of your mower, hence why it is not advised to run your mower without one.
The One Occasion You Can Run a Mower Without an Air Filter
The only time I would ever suggest running a lawn mower without an air filter is if you need to do so to try and diagnose a problem.
And even then you should make sure the mower isn’t moving, and you are running it purely for the purposes of troubleshooting.
Occasionally people will say their mower will only run when they have taken the air filter off.
But usually this either indicates a deeper problem with the mower or an air filter that is not fitted properly or is so clogged up it needs cleaning or replacing.
If you cannot work out what the issue is, take the mower to a professional.
It might set you back a bit more money in the short term, but it will save you a lot in the long term.
Can You Clean or Reuse Air Filters?
You certainly can clean or reuse air filters, but I would always advise that as a short-term fix to allow you to mow the lawn and you can then run into town afterward to get a new filter.
The fact is the filters in most lawn mowers are not designed to be cleaned, and they are so cheap to replace that spending a few dollars on a new filter is a much better option.
Most filters are made of paper or sponge that is not compatible with water or solvents.
If you need to clean your air filter to get a quick job done, the best way is to gently tap the filter on a hard surface to loosen the debris or use low-pressure compressed air to blow out any dirt.
Blow through the filter in the opposite direction to which the air usually flows when it is in place.
The continual use of compressed air, or compressed air at a high pressure can damage the filter by opening up its structure and allowing fine dirt particles into the engine, however.
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How Often Should You Change an Air Filter?
The frequency at which you change you air filter depends on your mower, how often you use it and the conditions in which you use it.
Your safest option is to follow the recommendations of the manufacturer of your lawn mower. Often they will recommend replacing the air filter every 25, 50 or 100 hours.
At the very least you should inspect your air filter annually at the end of each season and replace it if necessary.
If you mow in a sparse, sandy environment you will need to pay much closer attention to your mower’s air filter than if you mow lush, thick grass.
If in doubt, replace it.
As mentioned before air filters are not expensive for such a crucial part of a lawn mower.
Final Thoughts
Look at the infographic above and you can see it is a no-brainer really.
Can you run a lawn mower without an air filter? Of course you can, it is your lawn mower you can do whatever you want.
Should you run a lawn mower without an air filter? Nope, never.
Manufacturers state their mowers should not be used without an air filter.
Every gas mower you buy will come with an air filter installed.
They are there for a very important reason, to prevent the most vital part of your mower, the engine, from being seriously damaged.
Run your mower without an air filter just once, and one stray stone could wreck your mower.
Even the most expensive air filter isn’t more than $20, and the cheapest are around a dollar.
Running your mower without an air filter is a very expensive risk to take for such a small investment.