How to Tune Up Your Lawn Mower

This Old House landscape contractor Roger Cook shares his top five tips for keeping your lawn mower running smoothly

In this video, This Old House landscape contractor Roger Cook shares his top five tips for keeping your lawn mower running smoothly.


1. Check the mower’s oil level before every use. Be sure the mower is on level ground when checking the oil.
2. If the oil is low, add fresh oil to raise the level to the “full” line on the dipstick.
3. If the oil is dirty, change it by tipping the mower onto its side and draining the dirty oil into a container with a tight-fitting lid.
4. Recycle the old, dirty oil at a service station, auto shop, or local transfer station.
5. Add new oil a little at a time, stopping frequently to check the dipstick to avoid over-filling the crankcase.
6. Replace the air filter with a new filter every mowing season, or sooner if the mowing conditions are very dusty.
7. Change the spark plug once a year, or when the engine starts running rough.
8. Remove the old spark plug with a deep socket and ratchet wrench.
9. When installing the new spark plug, hand-thread it into place, then tighten it with the socket and ratchet. However, be careful not to over-tighten the spark plug or it will be difficult to remove next year.
10. Sharpen the blade every mowing season to ensure that it cuts the grass quickly and cleanly.   
11. Disconnect the spark plug wire to prevent accidental starting, then tip up the mower to gain access to the blade.
12. Use a ratchet wrench and socket to loosen the nuts that hold the blade in place.
13. Sharpen each end of the blade with a metal file or right-angle grinder. Be sure to maintain the blade’s original bevel angle, and remove the same amount of material from each end.
14. After sharpening, use a balancer to confirm that the blade is perfectly balanced.
15. If the blade is out of balance, file or grind the heavy end of the blade and then recheck it with the balancer.
16. To keep the mower running smoothly, always use fresh gasoline. Stale gas can damage the engine.
17. Buy only enough gas to last one month.
18. To extend the life of gasoline, add a fuel stabilizer.


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