Lawn Mower Oil Change

Doing a mower oil change especially on a modern mower is a gift, the manufacturers are making them so DIY user friendly, I doubt you’ll need a tool.

So when should you do a mower oil change? Lawn mower engine oil should changed at least once per season or every 50 hours of operation. Most engines will take a 1/2 quart (.6lt) of 10w30 engine oil.

If your yard is challenging terrain, hilly, over an acre, dusty, then a second oil change mid way through the season will help protect the motor. Clean the air filter regularly, about every 25 hours, more often in very dry dusty conditions. Ideally a mower needs a full tune-up at the start of the season and it’s only a little more work than an oil change.

This post covers the oil change and tune-up process, if need additional help check out “Mower tune-up video”. The video walks you through the whole process step by step. Easy oil draining technique, adding oil (type and quantity). It also covers plug change, air filter change, carburetor bowl draining and blade sharpening. You know, a complete pre season tune-up.

When to Tune-up

This is a question I get a lot. I tell my customers service your mower at the start of the new season before the first cut. Mowers that overwinter can often have issues that arise from being idle such as stale gas in the carburetor, sticking valves, sticking wheels, cables etc.

Maintenance infographic

If the storage area isn’t heated, moisture can collect inside the engine. That’s why I recommend a tune-up in the spring.

Proper winterizing will eliminate lots of problems, check out “Lawn mower winterizing”. If your mower is a tractor mower check out this guide “Riding mower maintenance”.

Modern mowers are user friendly, increasingly manufacturers are adding little features that make DIY repairs almost enjoyable. Features like: large easy to read dipstick; large fuel filler opening; fuel shut off valve; quick release air filter cover; carburetor fuel bowl drain plug; easy oil drain.
 
Knowing how to service and repair your own mower is a useful skill. Four stroke lawn mower engines are simple and most are designed thoughtfully, so that the home owner can easily DIY service.

Tune up kit

Tune-up Includes – Change engine oil; change plug; clean/replace air filter; fuel filter (if fitted); drain carburetor bowl; inspect and sharpen blades or replace; inspect drive belt; lube all axles and controls.

The Tools You Need

While doing an oil change likely won’t require any tools, a tune-up will require just basic ones. Doing a tune-up might sound like a lot of work, but really it isn’t. Its also not technical, and no special tools needed. Like many tasks, its about the right knowledge and good preparation.

Here’s a list of tools needed:

  • WD40
  • Socket set with plug socket
  • Selection of wrenches
  • Selection of screwdrivers
  • Torx drivers
  • Pliers
  • Inspection light
  • Flat file
  • Wire brush
  • Oil catch
  • Gloves
  • Goggles
  • Dust mask.
Tools

Check out all the tools I use here on the “Small engine repair tools” page.

Tune-up Parts You Need

Mower label

All engines will have a model code and date stamped. Briggs and Stratton stamp their codes into the metal valve cover at the front of the engine. Kohler have a tag and Honda have sticker on the body.

After you find these numbers, buying the tune-up kit on line is easy. Most mower engines are very common and so you won’t have a problem getting a tune-up kit to match.

 
Tune-up kit includes: oil; plug; air filter; fuel filter (if fitted); new blade (optional).
 
Check out part numbers with your engine maker.
 
Briggs and Stratton parts
 
Honda parts
 
Kohler parts
 
Kawasaki parts
 

Engine code

Engine Code – The engine code is useful info to have when ordering a tune-up kit.

Your mower may not be the same as the demo model but that’s not important, the process will be close to identical no matter what model you have. There are many different makes of mower and many are fitted with the very reliable Briggs and Stratton single cylinder engine. Kohler and Honda are also quite popular engines.

Tune-up Process

​Here’s the steped process, you don’t need to follow it in this order, this is just how I usually go about it. I do begin the process by warming the engine, it helps oil flow warm oil moves more freely than cold. warm oil also drains more quickly which helps bring all the contaminates with it.

Be sure to wear gloves and goggles when working with gas and do so in a well ventilated area. Remember to disable your mower by removing the plug wire before actually starting any work.

Note on blade sharpening: In this guide I do not remove the blade to sharpen. However, removing the blade to sharpen is best practice. The blade ideally, should be balanced after the sharpening process. An imbalanced blade leads to vibration.

All that said, when a blade is in good condition, it is acceptable to sharpen while remaining on the mower. Removing the blade comes with risks too, a blade must be tightened to manufacturers specifications. Too loose is obviously bad but too tight is problematic also.

A mower blade, coupled with a blade boss work together to help protect the crankshaft from damage. The blade is designed to slip on the boss in the event of a blade strike. This prevents crankshaft damage, over tightening the blade bolt, as you can imaging could be a costly mistake.

If you do choose to remove the blade to sharpen and balance or replace altogether, use a torque wrench to tighten. You’ll find video’s in the video library covering torque wrench use, sharpening, balancing and fitting blades and a ton of other repairs also. You’ll find a post here on the torque wrench I use.

Plug wire off

1 – Remove the plug wire (Twist & Pull) and leave it off until your ready to start the engine later in process.

Gas tap

2 – Turn off the gas tap, if fitted. Or pinch the gas line gently with a grips. When turning your mower over, always turn the carburetor side up.

Plug removal

3 – Remove and replace plug. Check that replacement plug is the same. Thread in new plug by hand before using the plug tool.

4 – Snug the plug down and give it a little tighten.. Not too tight! Don’t fit the plug wire just yet.

Gas filter

5 – Not all mowers will have a gas filter like this. Gas filters may be directional, and if so will have an arrow which points to the carburetor.

Gas line filter

Some filters will be built into the gas line, these type filters can be cleaned and reused.

Gas filter

Some gas tanks will have a filter mesh screen at the bottom. You may have to remove the tank to clean, depending how bad it is.

Air filter

6 – Remove & replace the air filter. Clean the air box being careful not to allow dirt into the carburetor.

Damage

7 – Check your blade for damage or excessive wear. If worn, replace. A new blade will be easier on the mower and your lawn. Never attempt to repair a bent blade, this will weaken the metal and can lead to injury.

Removing blade for sharpening and balancing is advised. If however, the blade is in good condition, you can sharpen in place. See replacing mower blades video here.

Blade sharpening

8 – We will sharpen this blade in place. It is however, always better to remove, sharpen and balance the blade before tightening to spec. An imbalanced blade leads to vibration.

Here’s we’ll file the face of the leading edge to remove any small nicks.

Blade sharpening

9 – Here, we’ll file at the same angle as the bevel, some blades will have the bevel facing the other way.

Blade sharpening

10 – Now dress the opposite side to remove the burrs. A sharp blade is the secret to a beautiful healthy lawn, and it extends the life of your mower.

Drive belt

11 – Most mowers will have a belt to drive the mower. Check the condition the belt and the pulleys.

Belt

These belts have a difficult job and can be the cause of various issues. Regular inspection will tell you if your belt is at the end of its life. Things to look for are flat-spotting, glazing, cracking and fraying.

Oil drain

12 – Drain the oil while the engine is still warm, this helps the draining process.

adding oil

13 – Add oil a little at a time, and check the level. Over filling is not good for the engine. It will cause oil leaks, misfiring and lots of smoke. Most small engine mowers will take a little over half a quart (.6lt) of 10w30 engine oil. Yes you can use car engine oil. See oil chart below.

Oil dipstick check

14 – Do not thread in dipsticks to check the level, just push in and remove to check. The full level on this dipstick is at the top of the hatched area.

Lube wheel

15 – Spray all controls with Wd40. Spray front & rear Axles also. WD40 lubes and protects from rust.

That’s it, Nice work!

Lawn mower oil chart

Related Question

How much oil does a push mower take? Most mowers will take about half a quart of oil or .6 of a liter from empty. Over filling will cause the engine to smoke.

Can I use 5w30 engine oil? 5w30 or 10w30 engine oil is good for a lawn mower engine.