How To Service A Petrol Lawn Mower

How To Service A Petrol Lawn Mower

A properly serviced and maintained petrol lawnmower can last a lifetime, making it well worth the investment. But where do you start? A brand new mower is usually fine for the first year or so – depending on usage – without much interference. But after this, at least once a year (ideally at the end of the cutting season) there are a number of things you need to do to keep your mower working at its best. So check out the list below for some top tips and pointers.


Changing the oil on a lawn-mower can be tricky. It needs to be done every now and again (roughly once a year, or every 50 hours of operation) but it’s important to do it right. Start by switching the engine on, to let the oil warm-up. After 60 seconds, turn the engine OFF again, disconnect the spark plug, and remove the dipstick. Then unscrew the oil plug and drain the old oil (to be disposed of safely), and refill the engine oil. On occasion, you may also want to replace the oil filter. 

Spark Plug

It’s a good idea to remove and clean the spark plug fairly often – perhaps once or twice a year, with some brake cleaner and a clean cloth.  Every few years (or when needed) you should replace the spark plug completely.  Be careful not to over tighten it when replacing, as you can accidentally close the spark gap, which will stop the engine from starting. 

The Blade 

Sharpening a lawnmower blade is a specialist skill and not something you should undertake unless you really know what you’re doing. Most people will remove the blade and take it to a lawnmower dealer after every 20-25 hours of use. For most domestic purposes, this will be about once a year. It’s also important to check the blade adaptor is aligned with the blade. The blade usually has two holes near the centre. Make sure these line up with the two notches on the adapter. 


Lawnmower wheels often have trims attached. In order to tighten the wheels, you need to remove the trims first (with a screwdriver). Tighten the wheels about once a year to make sure there is no excessive play in them, which may throw the mower off course and cause problems.


Cleaning and replacing your air filter is incredibly easy but very important. It will also help protect the carburettor and other areas of the mower from getting clogged.  Clean the filter every few times the mower is used, and replace it after two or three cleans. You can clean it by disconnecting the spark plug, removing the cover, and using some old fuel to remove dirt and dust.   

Petrol Tank

Draining and cleaning the petrol tank doesn’t need to be done often – about once a year will be more than enough – but will similarly help protect the mower from general wear. Just remove the tank, drain all remaining fuel, let the tank dry out, and then blow-dry with an air compressor or a can of compressed air. 

Looking for a new mower? Read our best petrol lawn mowers buyers guide



Hey, I'm Daniel. Having worked as a professional gardener for years as well as keeping a private allotment I decided to create this website to help spread my knowledge. I love gardening and hope to show you just how rewarding it can be!

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