A lawn mower is a machine with a small engine, a spinning blade, and a lot of moving parts operating in dirty, hot conditions. Like any machine, it needs regular maintenance. The good news is that the five most important tasks are simple, inexpensive, and can be done in your garage with basic tools. Here is what to do and how often to do it.
1. Keep the Blade Sharp
A dull blade tears grass instead of cutting it cleanly. Torn grass develops brown tips, is more susceptible to disease, and loses moisture faster. A sharp blade cuts cleanly, leaving a healthier lawn that looks better and recovers faster from mowing.
How often: Sharpen every 20 to 25 hours of mowing, or about once per season for a typical quarter-acre yard. If you hit rocks, branches, or roots, sharpen immediately.
How to do it: Remove the blade using a socket wrench (disconnect the spark plug first for safety). Use a blade sharpener tool or a bench grinder to restore the cutting edge to a 30-degree angle. Balance the blade using a blade balancer or by hanging it on a nail. An unbalanced blade causes vibration that damages the crankshaft bearing.
If the blade has deep nicks, cracks, or has been sharpened so many times that it is significantly shorter than original, replace it. A worn blade is a safety hazard.
2. Change the Oil Regularly
Engine oil lubricates the crankshaft, camshaft, and cylinder walls. Over time, oil breaks down and accumulates metal particles, carbon, and moisture. Running dirty oil accelerates wear on every internal engine component.
How often: Change oil after the first 5 hours of use on a new mower, then every 25 to 50 hours or once per season. Check the oil level before each mowing session.
How to do it: Run the engine for a few minutes to warm the oil, which helps it drain faster and more completely. Disconnect the spark plug. Tilt the mower with the spark plug facing up to prevent oil from flooding the cylinder. Remove the drain plug or use an oil extraction pump. Refill with the manufacturer-recommended oil type, typically SAE 30 for most push mowers or 10W-30 for colder climates.
Dispose of used oil at a recycling center or auto parts store. Never pour it down a drain or onto the ground.
3. Replace or Clean the Air Filter
The air filter prevents dust, grass clippings, and debris from entering the engine cylinder. A clogged filter restricts airflow, causing the engine to run rich (too much fuel, not enough air). This reduces power, increases fuel consumption, and can foul the spark plug.
How often: Check every 25 hours of use. Clean or replace as needed. Replace paper filters at least once per season. Foam filters can be washed and re-oiled several times before replacement.
How to do it: Remove the air filter cover (usually a plastic housing held by a snap or screw). For paper filters, tap them gently to remove loose dirt and hold them up to a light. If you cannot see light through the pleats, replace the filter. For foam filters, wash with warm soapy water, rinse thoroughly, let dry, and apply a small amount of air filter oil before reinstalling.
4. Clean the Underside of the Deck
Grass clippings, dirt, and moisture accumulate under the mower deck, creating a layer of compacted debris that traps moisture against the metal. This is the leading cause of deck rust and also reduces cutting efficiency by disrupting airflow that lifts grass for an even cut.
How often: After every mowing session, or at minimum once per month during the cutting season.
How to do it: Disconnect the spark plug. Tilt the mower with the spark plug facing up. Use a plastic scraper or putty knife to remove built-up grass. A deck wash attachment connected to a garden hose makes this easier. Simply attach the hose, run the mower for a few minutes, and the spinning blade flushes out debris.
For stubborn buildup, let the deck dry and use a wire brush. After cleaning, spray the clean deck with a light coat of WD-40 or silicone spray to inhibit rust.
5. Use Fuel Stabilizer for Seasonal Storage
Modern gasoline contains ethanol, which absorbs moisture from the air. When a mower sits unused for weeks or months, the ethanol separates from the gasoline and forms a corrosive layer at the bottom of the tank. This ethanol-water mixture damages carburetors, fuel lines, and injectors, and is the number one cause of mowers that will not start in the spring.
How often: Add stabilizer to every fuel purchase during the mowing season, and always add it before storing your mower for winter.
How to do it: Pour the recommended amount of fuel stabilizer into the gas tank, then fill with fresh gasoline. Run the engine for 5 minutes to circulate the treated fuel through the carburetor. For winter storage, either run the tank completely dry or fill it with stabilized fuel. A half-empty tank is the worst option because it allows the most condensation.
Bonus: Check the Spark Plug
While not in the top five, the spark plug is worth inspecting once per season. A fouled or worn plug causes hard starting, rough idling, and reduced power. Remove it, check the gap with a feeler gauge, and clean the electrode with a wire brush. Replace the plug every 100 hours or every two seasons. They cost under $10 and take 2 minutes to swap.
Build a Maintenance Schedule
Put these tasks on a calendar and they become routine rather than reactive:
- Each mow: Check oil level, clean deck
- Monthly: Check air filter, inspect blade
- Every 25 hours: Change oil, sharpen blade, replace air filter if needed
- End of season: Add fuel stabilizer, change oil, clean thoroughly, cover and store
Thirty minutes of maintenance per month will add years to your mower's life and keep your lawn looking its best. The tools and supplies you need, blade sharpeners, oil change kits, fuel stabilizer, and deck wash attachments, are all inexpensive and pay for themselves in the first season.
