The Complete Guide to Lawn Mower Oil

Some people learn it from their dads.  Some from their shop class.  Others from reading the manual.

Me?  I learned it the hard way.

I figured it out on my own.  I should have known better because my car needed it.  But I never put 2 and 2 together.  It never clicked for me.

But maybe I should back up.

When I bought my first house I suddenly had all these extra responsibilities that I never when I lived in an apartment.  Things like shoveling snow off the side walk, raking leaves and mowing the lawn.

And with those responsibilities come other responsibilities.  Like buying gas for the lawn mower,.  Or bringing leaves to the dump.

But with my new home ownership and all the responsibilities it entails, I never once thought about regularly servicing my lawn mower.

As I said, I should have known better.  I take my car into the shop every couple thousand miles after all.  Cars need their oil changed.  And filters changed.  And tires checked.  So why wouldn’t lawn mowers need the same thing?  Like I said … it never “clicked.”

So my mower worked fine for a while but after a number of years I started having problems.  Some times the mower wouldn’t start well.  Or there would be puffs of smoke where I was pretty sure they shouldn’t be.

And the the mower stopped running completely.  After yeas of neglect, it breathed its last breath.

Since that time I’ve become almost religious in how I upkeep my lawn mower.   And the results are obvious.  Regular maintenance and servicing have allowed me to keep the same lawn mower for about 15 years and it is still running strong.  To be honest I sometimes wish I had a nice, new lawn mower like my neighbors.  But the fact that I haven’t had to drop $1000 or more into a new riding lawn mower makes up for that.

A lot of you are probably like me 20 years ago – with no clue what to do about lawnmower maintenance.

And because of that, I wanted to write a tutorial on lawn mower oil.  Oil is one of the most important parts of your lawn mower and one of the things that needs regular maintenance in order to keep functioning properly.  Changing your oil regularly is THE number one thing you need to do to keep your lawnmower running well for a long time.

Below you’ll find answers to most of your questions about lawn mower oil, including what it does, why it’s needed and how to change it.

Why does my lawnmower need oil?

Your lawn mower engine is basically a hunk of metal with smaller moving metal parts inside it.  When metal moves past metal, it needs some sort of lubricant to prevent it from over-heating and to allow the engine to run smoothly.

Oil actually does a number of different things.  It keeps your engine cool.  It prevents build up of gunk inside the motor.

When should I change my lawnmower oil?

This varies based on the type of lawn mower you have but most manufacturers recommend changing the oil between 25 and 50 hours of use.

If you only use your lawnmower for mowing during the spring, summer and fall, this means you can usually get by changing your oil once a year.  This is what I do.  I typically change the oil right away in the spring after I take the mower out to be used for the first time that year.

If you mow a lot, then you may need to change the oil more often.  Then I would just change it every 25 hours.

How do I change the oil in my lawnmower?

  1. Make sure your mower is on a flat surface.
  2. Run your mower for 5 minutes or so.  This will warm the oil up and allow it to drain easier.
  3. Remove the dip stick.  You’ll want to take a rag and clean up around the dip stick so that no debris falls in.
  4. Drain the oil.  Different lawnmowers have different ways to drain the oil.  A lot of push mowers are designed to have the oil drained through the hole you pulled the dip stick out of.  You just tip the mower on its side and drain the oil into your oil pan.  A lot of push mowers will have a drain plug under the mower as well.  It is located under the mower by the blade and you will need a wrench to remove it.  For riding lawn mowers, there is usually a similar drain plug on the side of the mower.  Just  use your wrench to remove the plug and drain the oil into the oil pan.
  5. If you removed an oil plug, put it back in.  If you tipped your mower over, tip it back up on its wheels.
  6. Using a funnel, fill the mower back up with oil.  You don’t need a funnel but it can make things less messy. The amount of oil you need varies from manufacturer to manufacturer and based on the size of your mower.  Check your user’s manual if you have one.
  7. Dispose of your oil.  Most areas don’t allow you to just throw oil in the trash.  You can often just bring it to a local auto repair shop and they will take it free of charge.  I like to poor the used oil back into the oil cans that I just used to fill up my mower.

Tools I use for oil changes

You don’t need a lot of tools to change oil but a few basics will make the job a lot easier.

  • Oil pan – You need something to drain the oil into. It’s as simple as that. If you don’t have an oil pan already, you can get one for under $10. There are fancier ones, of course, but the simple one I linked to here is all you really need.
  • Funnel – As I said above, you don’t need a funnel but it can make things a lot less messy.   You can get a set of 4 different sizes for about $5 dollars.
  • Shop Towels – I use these Scott shop towels all the time when I’m working in the garage.  They are very heavy duty and rarely rip. Seriously, I couldn’t live without these.
  • Wrenches – You probably have a wrench already.  If you don’t, you can buy a nice set of wrenches for around $25.   The sizes you’ll get in that set will cover you fro 99% of the projects you would need them for.

That’s it.  You can get set up with all of these for less than $50, which is way cheaper than bringing your mower into somebody to change the oil for you.

What do the numbers on an oil bottle mean?

Oil manufacturers make all different types of oil.  The numbers on the can of oil tell you what type it is.  The numbers usually look like 10W-40 or SAE 30 or something similar.

These numbers refer to the viscosity of the oil.  Viscosity has to do with how thick a liquid is.  So water is less viscous than honey.  And chocolate syrup is less viscous than peanut butter.

So if you see oil that says SAE 30 or SAE 40 on the side of the can, that is just a number referring to the oil’s thickness.  SAE stands for Society of Automobile Engineers.  They’ve come up with standards for how to rate oil viscosity so that you can compare one brand of oil to another.

So what does the “W” mean?  It has to do with temperature.  You may have noticed that if you heat up chocolate syrup or spaghetti sauce that they get a lot thinner.  Heat tends to make liquids less viscous (thinner) and cold tends to make liquids more viscous (thicker).

So when you see oil that says “10W-30”, its telling you something about how the oil acts in hot and cold temperatures.  “W” actually stands for “winter.”  A 10W-30 or a 5W-30 will act like a SAE 30 at warm temperatures.  But at cold temperatures a 10W-30 will act like an SAE 10 and a 5W-30 will act like an SAE 5 oil.

What kind of oil should I use in my lawn mower?

This is a complicated question and depends on a lot of factors.  If you have your users manual for your mower, you should always use what they recommend.  But it will also depend on where you live and what the climate is like when you use your mower.

For example, if you use your mower with a snow blower attachment in the winter, you will probably want to use a winter grade oil.  But if you only use the mower during the spring, summer and fall to mow the lawn, then you might get buy with a non-winter grade.

SAE 30 is usually a safe bet if you don’t have a manual and you only use the mower during warmer whether.  If you use your lawnmower all year round, then 10W-30 is usually what you want to go with.

2 cycle engines vs 4 cycle engines

One last thing I should talk about before I end this post.  Not all lawn mower engines require oil changes.  A lot of smaller engines require you to mix the oil in with the gas every time you fill your gas tank up.

The type of engine I’ve been talking about throughout this post was the 4 cycle engine.  The gas and oil are separate and shouldn’t be mixed.

On the other hand, 2 cycle engines will require a mixture of oil and gas to be put in the gas tank.  The mix ratio for these motors is usually something like 50:1 or 30:1.  It varies by type of engine and should be found in your user’s manual.

For 2 cycle engines, you should make sure you buy a 2 cycle oil.  This type of oil is specially made for 2 cycle engines.

This ratio is the gas to oil ratio that your engine needs.  So 50:1 requires 50 parts gas and 1 part oil.  Most 2 cycle engine oils will tell you how to mix different ratios on the oil can.



That’s it for my tutorial on lawnmower oil.  The main thing to remember is that oil changes are a very important maintenance item that everybody should perform regularly.  If you’ve never changed oil before, I hope the steps above will help you out.

Also, let me know in the comments if you found it useful or if you have any questions.



Leave a Reply

Your email address will not be published. Required fields are marked *