By: Author John Cunningham. Published: 2018/12/08 at 9:03 am
Doing a mower oil change, especially on a modern mower, is a gift; the manufacturers are making them so DIY and user-friendly that I doubt you’ll need a tool.
So when should you do a mower oil change? Lawnmower engine oil should change 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, or 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 you 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 to service their mowers 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.
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 homeowner can easily DIY service.
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. It’s also not technical, and no special tools are needed. Like many tasks, it’s about the right knowledge and good preparation.
Here’s a list of tools needed:
- Socket set with plug socket
- Selection of wrenches
- Selection of screwdrivers
- Torx drivers
- Inspection light
- Flat file
- Wire brush
- Oil catch
- Dust mask.
Check out all the tools I use here on the “Small engine repair tools” page.
Tune-up Parts You Need
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 has a tag, and Honda has a sticker on the body.
After you find these numbers, buying the tune-up kit online is easy. Most mower engines are common, so you won’t have a problem getting a match-tune-up kit.
The tune-up kit includes oil; plug; air filter; fuel filter (if fitted); new blade (optional).
Check out part numbers with your engine maker.
Engine Code – The engine code is useful information 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 mowers, and many are fitted with the very reliable Briggs and Stratton single-cylinder engine. Kohler and Honda are also quite popular engines.
Here’s the stepped process; you don’t need to follow it in this order; this is how I usually do it. I do begin the process by warming the engine; it helps the oil flow. Warm oil moves more freely than cold. Warm oil also drains more quickly, which helps bring all the contaminants 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.
I’ve covered it in video format, also. You’ll find the video here on “Tune-up video.”
Note on blade sharpening: In this guide, I do not remove the blade to sharpen. However, removing the blade to sharpen is the 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 it while remaining on the mower. Removing the blade comes with risks, too; a blade must be tightened to the manufacturer’s specifications. Too loose is obviously bad, but too tight is problematic, also.
A mower blade, coupled with a blade boss, works 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 imagine, could be a costly mistake.
If you do choose to remove the blade to sharpen and balance or replace it altogether, use a torque wrench to tighten it. You’ll find videos 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.
1 – Remove the plug wire (Twist & Pull) and leave it off until you are ready to start the engine later in the process.
2 – Turn off the gas tap if fitted. Or pinch the gas line gently with grips. When turning your mower over, always turn the carburetor side up.
3 – Remove and replace the plug. Check that the replacement plug is the same. Thread in the new plug by hand before using the plug tool.
4 – Snug the plug down and give it a little tightening. Not too tight! Don’t fit the plug wire just yet.
5 – Not all mowers will have a gas filter like this. Gas filters may be directional and will have an arrow pointing to the carburetor.
Some filters will be built into the gas line; these types of filters can be cleaned and reused.
Some gas tanks will have a filter mesh screen at the bottom. You may have to remove the tank to clean it, depending on how bad it is.
6 – Remove & replace the air filter. Clean the air box being careful not to allow dirt into the carburetor.
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 the blade for sharpening and balancing is advised. If the blade is in good condition, you can sharpen it in place. See replacing mower blades video here.
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 we’ll file the face of the leading edge to remove any small nicks.
9 – Here, we’ll file at the same angle as the bevel; some blades will have the bevel facing the other way.
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.
11 – Most mowers will have a belt to drive the mower. Check the condition of the belt and the pulleys.
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.
12 – Drain the oil while the engine is still warm; this helps the draining process.
13 – Add oil a little at a time, and check the level. Overfilling 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 the oil chart below.
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.
15 – Spray all controls with WD40. Spray front & rear Axles also. WD40 lubes and protects from rust.
That’s it. Nice work!
About the Author
John Cunningham is a Red Seal Qualified automotive technician with over twenty-five years experience working on all types of equipment, grass machinery, ATVs, Dirt bikes, cars, and trucks. When not writing how-to articles, he may be found in his happy place – Restoring classic machinery.
You may find the following links helpful:
- Riding mower maintenance & repair index
- Walk behind mower maintenance & repair index
- Recommended tools & parts
- Recommended mowers
- Repair videos
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. Overfilling will cause the engine to smoke.
Can I use 5w30 engine oil? 5w30 or 10w30 engine oil is good for a lawnmower engine.
- About the Author
- Latest Posts
John Cunningham is an Automotive Technician and writer at Lawnmowerfixed.com.
He’s been a mechanic for over twenty-five years and shares his know-how and hands-on experience in our DIY repair guides.
Johns’s fluff-free How-to guides help homeowners fix lawnmowers, tractor mowers, chainsaws, leaf blowers, power washers, generators, snow blowers, and more.