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DIY Rotary Mower Servicing: Cut Costs, Cut Grass!

Writer's picture: John CJohn C

Updated: Dec 19, 2024


 JC changing the oil on a mower A person named JC is emptying a mower of oil. The person is holding a drain pan under the mower to catch the used oil.
JC tipping the old oil from a rotary lawn mower into a homemade modified drip tray on a well-maintained lawn.


If you own a small rotary petrol mower, regular servicing is key to keeping it running smoothly and ensuring a healthy lawn. But you don't have to break the bank to keep your mower in tip-top shape. With a little know-how, you can save money by servicing your mower yourself. Here's how:



What You’ll Need for a Simple Lawn Mower Service:


💧 Engine Oil

Make sure to use the right oil. This SAE 30 Engine Oil is perfect for most rotary petrol mowers.



💡 Tip: Always check your mower’s manual in case it requires a different oil type.



 

💨 Air Filter

A clean air filter improves performance and keeps your engine running smoothly. If you’re unsure of your exact model, I use this type of filter or check for one that’s compatible with your mower.



 


Spark Plug

A fresh spark plug ensures smooth starts. I recommend this spark plug, which works with many popular mowers.



💡 Double-check your manual to confirm the correct part number before buying.



 

🛠 Wrench and Rag

A simple spark plug wrench set and a rag will help you get the job done quickly and cleanly.




 


A lawn mower in JCs  garden. With all the service parts. Oil, Air Filter, Spark Plug and oil
Basic essential servicing parts next to rotary mower. Oil, Air filter, spark plug and oil drip tray.


For a basic service get some oil, air filter and spark plug. Changing these once a year could enhance the reliability for many years.

Yellow warning sign with an exclamation mark symbol

Disconnect the spark plug to ensure your safety before beginning any maintenance work. This is usually a push-on / pull-off connector.



 


🛠 Quick Oil Check


  1. Wipe the Dipstick: Use a clean rag to wipe it before inserting it back into the engine.


  2. Check the Oil Level:


    • Color: Clean oil looks like clear, runny honey.


    • Feel: Smooth, not gritty.


    • Black or Gunky? It’s time for an oil change.



 


Red oil can with a spout and dripping oil, representing the oil change process for a lawn mower.

Changing the Old Mower Oil




Locate the Oil Drain Plug


  • On most mowers, it’s on the side of the engine.

  • On my Honda mower, the oil drain plug is the same as the oil top-up point.



Position a Container


  • Place a container underneath the drain plug to catch the old oil.

  • Pro tip: Have a practice run turning the mower on its side before removing the drain/fill plug. It’ll save you from missing the container!



Drain the Oil


  • Once ready, be quick and turn the mower swiftly onto its side. The oil will drain out fast your homemade drip tray.


⚠️ If you hesitate or turn the mower too slowly, you risk oil spilling onto the outside of the engine and deck, creating a mess and extra cleanup.




💡 Next Step:

  • Once the oil is in the tray, carefully pour it into an empty old milk bottle or a similar container. This makes it easy to transport the old oil for proper disposal at your local recycling center.



Replace the Old Oil


  • I replace the oil with fresh, clean SAE 30 oil once a year—a simple habit that has kept my mower running smoothly for over 15 years!




 



💡TIP: Create your own cheap oil drip tray with this 4 litre bottle hack.




 


fitting a new air filter to a rotary lawn mower.
Fitting a new rotary mower air filter


  • Replacing the old mower air filter. The air filter prevents dust and debris from entering the engine, which could cause engine damage or rough running of the engine if it becomes clogged. I replace the air filter with a new one, once every year.






Removing  a mower spark plug with a socket ratchet.
Removing a spark plug from a rotary mower


  • Remove and Inspect the spark plug for wear and tear.



New spark plug (left) vs. old spark plug (right)
New spark plug (left) vs. old spark plug (right)


  • Check and replace it if necessary. This is an essential component that provides the spark needed to ignite the fuel in the engine. I replace the old spark plug with a new one once every year.



Underneath a rotary lawn mower that requires a clean.
Underneath a rotary lawn mower that requires a clean.

⚠️ Warning:


Never tip your rotary mower on its side with the air filter facing the floor. Doing so can cause oil to leak into the air filter, leading to poor engine performance. Instead, tilt the mower backward or to the side with the air filter facing up.


 


Further Reading


🛠 Keep Your Mower in Top Shape


Don’t overlook the importance of a sharp blade! Check out my mower blade sharpening guide to ensure your lawn gets the cleanest cut possible.


  • Check the blades for damage or dullness, and sharpen or replace them if necessary. Dull blades can lead to an uneven cut and damage to your lawn. Also, give the underside of the mower a clean and scrape off any stuck on old muck or old grass. This helps with the collection and flow of grass going into the grass collecting box.



 


Need to Sharpen Your Blade?


A sharp mower blade ensures a clean cut and a healthy lawn. Follow my step-by-step guide to sharpening your mower blade to get the job done right!



 


Protect Your Mower Deck!


Whether your mower deck is plastic or metal, prevent rust and buildup with ease. Check out my blog on protecting your mower deck with WD-40 PTFE Dry for tips on keeping it in top shape.



 


To Wrap It Up


Servicing your small rotary petrol mower yourself can save you money and ensure a healthy lawn and mower. With these simple steps and photos, you can easily maintain your mower and keep your lawn looking its best.



Thanks for supporting JC in the Shed! Some of the links above are affiliate links, which means I earn a small commission if you make a purchase—at no extra cost to you. Every little bit helps keep this content coming!



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About - Created by a dedicated DIY & gardening enthusiast, proudly holding a City & Guilds Level 2 Certificate in Agriculture - JC

 

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