Winterizing Your Lawn Mower

Winterizing Your Lawn Mower

A properly winterized mower starts reliably in spring and avoids costly repairs. The key is to do this before the first hard freeze—ideally when nighttime temperatures consistently drop below 40°F (4°C), and you’ve mowed for the last time. This guide covers the steps, with specific timing, temperatures, and mower-height advice.

When to Winterize

Timing: Aim for mid-to-late October in most northern climates, or after the last mow of the season. For warm-season grasses (Bermuda, Zoysia), winterize after the final mow when grass stops actively growing—usually after the first frost. For cool-season grasses (Fescue, Bluegrass), winterize after the last mow when growth slows, typically when soil temps drop below 50°F (10°C).

Temperature rule: If the forecast shows 7 consecutive nights below 32°F (0°C), it’s time. Don’t wait until snow is on the ground—fuel stabilizer needs time to circulate.

Step 1: Final Mow and Deck Cleaning

• Mower height: For the last mow, lower the deck by one notch (about 0.5–1 inch) below your normal summer height. This prevents matted grass and reduces disease risk over winter. For cool-season lawns, keep it at 2–2.5 inches; for warm-season, 1–1.5 inches.
• Clean the deck: After mowing, scrape off all grass clippings, mud, and debris from the underside of the deck. Use a plastic scraper or a pressure washer (avoid blasting seals). Wet grass left on metal causes rust and corrosion.
• Dry it: Let the mower sit in a dry, ventilated area for 30 minutes so the deck dries completely.

Step 2: Fuel System Protection

Gasoline degrades in 30 days. Stabilize or drain.

• Option A: Add fuel stabilizer (recommended for most users)

  • Fill the tank with fresh, ethanol-free gasoline (if available).
  • Add a stabilizer like STA-BIL or Sea Foam, following the label ratio (typically 1 oz per 2.5 gallons).
  • Run the engine for 5–10 minutes to circulate the stabilized fuel through the carburetor.
  • Then top off the tank to prevent condensation. Leave the tank full (not empty) to minimize air space.

• Option B: Drain the fuel (for long storage or ethanol issues)

  • Run the mower until the tank is empty and the engine stalls.
  • Drain the carburetor bowl (locate the small screw or drain plug underneath). Collect fuel in a container and dispose properly.
  • This is safer if you store the mower in a shed that freezes—stabilized fuel still absorbs moisture over 4–6 months.

Temperature note: If you store the mower in an unheated garage or shed that dips below 0°F (-18°C), use ethanol-free fuel + stabilizer. Ethanol attracts water, which can freeze and crack the carburetor.

Step 3: Oil Change

Dirty oil contains acids that corrode engine parts over winter.

• When to change: After the final mow and fuel stabilization, with the engine warm (run it for 5 minutes). Warm oil drains faster and carries out contaminants.
• Procedure:
  • Place a drain pan under the oil drain plug (or tip the mower on its side, carb side up).
  • Remove the plug, let oil drain completely (about 2–3 minutes).
  • Reinstall the plug, then refill with the manufacturer-recommended oil weight (usually SAE 30 or 10W-30 for small engines).
  • Check the dipstick—don’t overfill.
• Disposal: Take old oil to an auto parts store or recycling center.

Step 4: Spark Plug and Air Filter

• Spark plug: Remove it with a socket wrench. Inspect for carbon buildup or cracks. If the electrode is worn or the gap is off (check manual for spec), replace it. A new plug costs $5–10 and ensures easy starting in spring.
• Air filter: Clean or replace. Foam filters: wash with soapy water, dry, and re-oil. Paper filters: tap out dust or replace if dirty. Never run a mower without a filter—dust will ruin the engine.

Step 5: Blade Care

• Sharpen or replace: Remove the blade (wear gloves). Sharpen with a file or grinder, or take it to a shop. A dull blade tears grass, causing brown tips. If the blade is bent or nicked, replace it.
• Balance: After sharpening, hang the blade on a nail—if one side drops, file the heavy side. An unbalanced blade vibrates and damages the spindle.
• Reinstall or store: If you’re not storing the mower in a heated space, wipe the blade with a light coat of oil to prevent rust.

Step 6: Battery (If Electric Start)

• Disconnect: Remove the negative terminal first, then the positive.
• Store: Keep the battery in a cool, dry place above freezing (basement or heated garage). Do not leave on concrete—place on wood or a shelf.
• Charge: Give it a trickle charge every 4–6 weeks to prevent sulfation. A battery tender is ideal.

Step 7: Final Storage

• Position: Park the mower on a flat, dry surface. If possible, elevate it on blocks to keep tires off cold concrete (prevents flat spots).
• Cover: Use a breathable mower cover or an old sheet—plastic traps moisture.
• Location: Store in a shed or garage that stays above 20°F (-6°C) if possible. If unheated, ensure fuel is stabilized and battery is removed.

FAQ

Q: Can I skip the fuel stabilizer if I run the mower dry?
A: Yes, but draining the carburetor bowl is critical. Even empty tanks can have residual fuel that gums up jets. If you drain, also spray carb cleaner into the fuel inlet.

Q: My mower has a plastic deck—do I still need to clean it?
A: Yes. Grass clippings hold moisture against plastic, causing mold and warping. Scrape thoroughly.

Q: Should I store the mower with the blade on or off?
A: On is fine—just make sure it’s sharpened and oiled. If you remove it, label the bolts so you don’t lose them.

Q: What if I live in a mild climate (no hard freeze)?
A: You can skip fuel stabilizer if you mow year-round, but still clean the deck and change oil every 50 hours of use.