Lawn Mower Maintenance: Schedule by Hours for Walk-Behinds and Riders

Lawn mower maintenance is the routine care of the engine or motor, blade, deck and drive that keeps a mower starting, cutting cleanly and running safely. For a gas mower that means oil, air filter, spark plug, fuel and blade care. Riding mowers and zero-turns add an oil filter, fuel filter, belts, grease fittings, tires, a 12-volt starting battery and, on some models, transmission service. Battery mowers drop all the engine work but still need blade, deck and battery care.

Most homeowners mow 20 to 40 hours a season on a walk-behind and more on a rider for larger properties, so many hour-based jobs line up with once or twice a year. Do whichever comes first, the hours or the season.

Walk-behind mowers often have no drain plug. Run the engine a few minutes so the oil flows, shut it off, disconnect the spark plug wire and let the muffler cool. Then either use an oil extractor pump through the fill tube, or tip the mower the way the manual shows, usually with the air filter and carburetor side up so oil does not soak the filter, and drain through the fill tube into a pan. Refill slowly with the oil the manual lists (commonly SAE 30 for warm weather or 10W-30 for varying temperatures) to the full mark. Capacities are small, often about a pint or less, so add a little at a time and check the dipstick.

Riding mowers and zero-turns usually have a drain valve or hose. Warm the engine, park on level ground, set the brake, remove the key, and drain into a pan. Replace the oil filter if due, wiping a film of fresh oil on the new gasket and tightening by hand as directed. Refill to the full mark and check for leaks. Recycle used oil and filters at an auto parts store.

Clean or check it every 25 hours and replace a paper filter at least once a year, more often if you mow dry, dusty or sandy lawns or collect leaves. A clogged filter starves the engine of air, which causes hard starting, black smoke, lost power and wasted fuel. A torn filter is worse, because dirt goes straight into the engine.

Tap paper cartridges gently to remove loose dirt; do not blow compressed air through them or wash them. Foam pre-cleaners and foam filters can be washed in warm soapy water, rinsed and dried completely, and lightly oiled only if the manual says so. Never run the engine without the filter installed. Buy the exact filter part number for your engine model.

Replace it once a year or every 100 hours, and inspect it whenever the mower is hard to start. A replacement spark plug costs a few dollars; use the exact plug listed in your manual and set the gap with a feeler gauge. V-twin riders have two plugs, so replace both.

The old plug tells you something. Light tan deposits are normal. Black, dry soot points to a dirty air filter or a rich mixture. Wet, oily deposits can mean overfilled oil or a mower tipped the wrong way. Remove and install the plug only with the engine cool, and thread it in by hand before tightening so you do not cross-thread the aluminum head.

First make the mower safe: engine off, key out, and spark plug wire disconnected, or battery and safety key removed on a battery mower. Wear heavy gloves.

1. Get access. Tip a walk-behind with the air filter and carburetor side up, as the manual directs. Raise a rider with a lift such as the MoJack EZ MAX 45001 Riding Mower Lift, which raises the front 24 inches and handles 450 pounds, or the drive-on MoJack ZR350 45005 Riding Mower Lift for lighter riders. Follow the lift's instructions, chock the wheels and set the parking brake. Never work under a mower held only by a jack.
2. Mark and remove. Mark the bottom of the blade with paint, block it with a piece of wood and remove the bolt.
3. Sharpen. Clamp the blade in a vise and file or grind along the original cutting angle, removing equal metal from both ends. Stop at a clean, even edge; a razor edge chips quickly. Keep a grinder moving so the steel does not overheat and turn blue.
4. Balance. Hang the blade on a blade balancer or a nail. If one end drops, take a little more off that end until it hangs level.
5. Replace instead if the blade is bent, cracked, or worn thin at the curved lift section.
6. Reinstall the correct side down and tighten the bolt to the torque in the manual.

For Husqvarna 48-inch riders, OEM Husqvarna 48 in. Mulching Blades (3 Pack) ($31.95) or Husqvarna 48 in. High-Lift Bagging Blades (3 Pack) are inexpensive enough that many owners keep a spare set sharpened and swap them in.

Clean the deck after each mow, while the clippings are still soft. With the engine off, the blade stopped and the spark plug wire disconnected, scrape caked grass from the underside with a plastic scraper or putty knife. Built-up grass blocks airflow, which ruins the lift that mulching and bagging depend on, and it holds moisture against the steel.

Many mowers have a deck washout port that connects to a garden hose; the YARDMAX YG2860 22 in. Select PACE Self-Propelled Gas Mower, 201cc, for example, lists a deck cleanout port. Follow the manual on running the blade while using it. Do not pressure wash the engine, bearings or electrical parts. Battery mowers vary by water rating: the Greenworks 60V 21 in. Push Mower Kit lists an IPX4 steel deck, which resists splashing, and the EGO POWER+ LM2206SP 22 in. Aluminum Deck Self-Propelled Mower Kit uses a cast aluminum deck that will not rust. Brush them clean rather than hosing unless the manual allows it.

• Belts: with the engine off and the key out, check the deck and drive belts for cracks, fraying, glazing and missing chunks. A squeal, burning smell or a deck that bogs down in normal grass points to a worn or loose belt. Replace with the manual's part number and follow the belt routing diagram.
• Tires: set pressure to the sidewall or manual figure; front and rear usually differ. Uneven pressure makes the deck cut unevenly and hurts traction on slopes.
• Grease: grease the spindles, front axle and pivots that have fittings at the manual interval. Wipe the fitting first so you do not pump dirt in.
• Transmission: some zero-turn transaxles are serviceable, such as the Hydro-Gear ZT-3100 on the Husqvarna MZ61 61 in. Zero Turn Mower with ROPS; follow the manual's fluid and filter interval.
• 12V battery: clean corroded terminals and keep the battery charged in storage with a maintainer such as a Battery Tender Junior.

Much less than gas, but not none. Sharpen or replace the blade on the same 20 to 25-hour schedule, clean the deck after each mow, and keep the wheels and height adjusters free of packed grass. Electric riders like the EGO POWER+ T6 TR4204 42 in. Electric Lawn Tractor list belt-free blade motors, which removes deck belts from the list.

Battery care matters most, because the pack is the costliest part. Let a hot pack cool before charging, charge it on the maker's charger indoors at room temperature, store it indoors out of heat and freezing, and follow the manual on storage charge level. Never charge or use a battery that is swollen, cracked, leaking or damaged; take it to a battery recycling drop-off. Always remove the battery and safety key before touching the blade.

Yes, in any fuel that will not be used within about a month. Gasoline starts to degrade within weeks, and ethanol-blended fuel absorbs moisture, which leads to varnish in the carburetor, hard starting and surging, the most common small-engine repair. Many engine makers advise using untreated fuel within about 30 days.

• Add a stabilizer such as STA-BIL Storage to the can when you buy the fuel, not months later.
• Use regular unleaded with no more than 10 percent ethanol. The EPA prohibits E15 in lawn mowers and other outdoor power equipment.
• Store fuel in an approved container such as a No-Spill gas can, away from living spaces, pilot lights and sunlight.
• Refuel only with the engine off and cool, outdoors, and wipe up spills before starting.

1. Fuel: stabilize a full tank and run the engine so treated fuel reaches the carburetor, or drain and run it dry, exactly as the manual directs.
2. Oil: change it so acidic combustion residue does not sit in the engine all winter.
3. Blade: sharpen or replace it now, so the mower is ready on the first spring mow.
4. Deck: scrape and clean it, and touch up bare steel.
5. Batteries: bring battery-mower packs indoors; put riders' 12V batteries on a maintainer or remove them.
6. Cover and store: park in a dry, ventilated space away from pilot lights. A fitted cover such as the Husqvarna 54 in. Full-Size Lawn Tractor Cover or EGO POWER+ CRM001 Riding Mower Cover keeps dust and moisture off riders stored in sheds or carports.

Short on storage? The shed size for a riding mower page shows the footprint a rider really needs.

Routine parts such as blades, filters, plugs, belts and a carburetor cleaning are almost always worth doing. Replacement makes more sense when a budget push mower needs an engine rebuild, when the deck has rusted through, or when repairs would cost more than half the price of a comparable new mower.

If it is time, buy for your lawn rather than repeating the old mower. Battery walk-behinds like the EGO POWER+ LM2135SP 21 in. Select Cut Self-Propelled Mower Kit eliminate oil, filters, plugs and fuel entirely; see the best battery lawn mowers. For an acre or more, a rider such as the Husqvarna Z254F 54 in. Zero Turn Mower with a fabricated deck is built for years of service; see the best zero-turn mowers.