A lawnmower is a significant investment for most homeowners, yet it often gets minimal care. The good news is that most mower problems are preventable. With regular maintenance your machine will start first time, cut cleanly and last far longer than the warranty.
Why lawnmower maintenance matters
Neglect creates cascading problems. Blunt blades tear grass rather than slice it, leaving frayed, browning tips that invite disease. Clogged air filters and fouled spark plugs force the engine to work harder and burn more fuel. Look after a mower properly and it can easily last fifteen to twenty years.
Safety matters too: blades spin at dangerous speeds, so regular inspection is essential.
Safety first: always isolate the power
Before you touch the underside of any mower, disconnect the power source:
- Petrol mowers: Remove the spark plug cap.
- Cordless mowers: Remove the battery and safety key.
- Corded electric mowers: Unplug from the mains socket.
Always wear sturdy gloves when handling blades.
The basic maintenance kit
You will need cut-resistant gloves, safety glasses, brushes, a metal file or blade sharpener (roughly £20 to £40 for guided models), a socket set, and the right engine oil, spark plugs and air filters for your machine.
Step 1: Clean your mower after every cut
Regular cleaning prevents rust and keeps the cut quality high. Isolate the power, tip the mower onto its side, scrape caked grass from the underside of the deck and wipe down all surfaces. Avoid pressure washers on petrol models.
Step 2: Sharpen or replace the blade
Sharpen the blade every 20 to 25 hours of mowing, or at least once a season for an average UK garden. Frayed or whitish grass tips are the visual sign of a dull blade.
- Mark the underside of the blade with paint so you refit it the right way up.
- Remove the central bolt.
- Clamp the blade in a vice.
- File along the existing bevel at about 30 degrees.
- Sharpen each end equally to keep the blade balanced.
- Refit and tighten securely.
Replace blades that are cracked, bent or worn thin rather than sharpening them.
Step 3: Check and change the oil (petrol mowers)
Four-stroke engines need clean oil. Check the dipstick before every few uses. Most UK mowers use SAE 30 in summer, or 10W-30 as an all-season alternative. Change the oil after the first five hours on a new machine, then roughly every 25 hours or once a season.
To change it, warm the engine, drain the oil into a tray through the drain plug or dipstick tube, refill slowly to the correct level, and take the old oil to a recycling centre.
Oil we’d use: Briggs & Stratton SAE 30 4-Stroke Engine Oil, 600ml
A straightforward single-grade summer oil that suits most four-stroke petrol mowers, and the 600ml bottle is about right for a typical seasonal top-up or change. Check your handbook first in case your engine specifies a different grade.
Key specs: SAE 30, four-stroke, 600ml bottle. See card for current price.
Step 4: Look after the spark plug (petrol mowers)
Inspect the plug once a season. Pull off the cap and unscrew it with a spark-plug spanner. A healthy plug is light tan or grey. Black, sooty or oily plugs point to poor running and need cleaning or replacing. Tighten a replacement until you feel resistance, then add a quarter turn.
Step 5: Service the air filter (petrol mowers)
Check the air filter every few uses in the cutting season. Foam filters can be washed in warm soapy water, dried completely and lightly oiled before refitting. Paper filters should be tapped clean and replaced yearly. Never run the engine without a filter.
Step 6: Manage the fuel
Modern petrol can degrade within a month or two as it absorbs ethanol and moisture. Buy fuel in small quantities, add a fuel stabiliser for winter storage, and run the tank nearly dry at the end of the season to stop stale fuel gumming the carburettor.
Maintaining cordless and corded electric mowers
Cordless battery mowers
Store batteries indoors somewhere cool and dry, keep the contacts and cooling vents clean, charge fully before the first cut of the year, and top up every couple of months over winter.
Corded electric mowers
Inspect the cable before every use for cuts, nicks or exposed wire, always use an RCD, and keep motor vents clear. Store in dry conditions to protect the windings.
Both types need blade sharpening in the same way as petrol models.
A year-round maintenance schedule for the UK
|
Season |
Tasks |
|
Spring (Mar–Apr) |
Full pre-season service: oil change, new spark plug and air filter, blade sharpening, battery charging, fuel freshness check, test-start |
|
Summer (May–Aug) |
Post-cut cleaning, regular oil level checks, blade maintenance, vent clearing |
|
Autumn (Sep–Oct) |
Raise cutting height, final cleaning, fuel run-down |
|
Winter (Nov–Feb) |
Empty or stabilise fuel, clean deck, store batteries indoors, keep machine dry and covered |
Winterising and storing your mower
Autumn storage decides spring starting. Clean the mower thoroughly, sharpen the blade, sort out the fuel, lightly oil bare metal under the deck, take batteries indoors, and store the mower somewhere dry, off bare flooring and covered.
Common problems and quick fixes
The mower will not start: On petrol models check for stale fuel, a fouled spark plug and a clogged air filter. On cordless models check battery charge and seating. On corded models check the cable, plug and RCD.
The engine runs but cuts out: Usually a dirty air filter, blocked fuel line or a deck packed with wet grass.
The cut looks ragged or uneven: A blunt blade is the most likely cause, followed by uneven cutting height or grass build-up under the deck.
White or blue smoke: Typically oil where it shouldn’t be, often from overfilling or tipping the mower the wrong way.
When to call a professional
Internal engine work, carburettor rebuilds, starter-cord replacement and electrical faults are best left to a professional. Many dealers offer winter servicing during their quieter months.
Frequently asked questions
How often should I sharpen my mower blade?
Around every 20 to 25 hours of use, or at least once a season for a typical garden.
What oil does my petrol lawnmower need?
Most four-stroke mowers use SAE 30 in summer, or 10W-30 as an all-season alternative. Check your handbook.
Can I jet-wash my lawnmower?
It is best to avoid pressure washers on petrol models, as water can get into the engine and bearings. Use a scraper and brush instead. Keep water away from motors and battery contacts on cordless and corded models too.
Do electric mowers need any maintenance?
Less than petrol models, but they still need blade sharpening, deck cleaning and battery or cable care.
Final thoughts
Good mower care comes down to habits: clean after each use, keep the blade sharp, use fresh oil, check the spark plug each season and store the machine sensibly over winter. Do that and it will run sweetly for many years, with far less troubleshooting.
