How to winterize your lawn mower

Gas left sitting all winter is the single most common reason a mower won't start in spring. Ethanol pulls in moisture and gums up the carburetor. You have two good options: add fuel stabilizer to a full tank and run the engine five minutes so treated fuel reaches the carburetor, or run the tank completely dry and then run the engine until it stalls. Pick one — half a tank of untreated gas is the worst case.

Used oil carries acids and combustion grit that eat at the engine over a long idle period. Run the mower a couple of minutes so the oil thins, shut it off, disconnect the spark plug, then drain and refill with the weight in your manual (usually SAE 30 or 10W-30). Dispose of the old oil at an auto parts store.

A dull blade tears grass instead of cutting it, which browns the tips and stresses the lawn. Winter is the easiest time to do it because you're not losing a mowing weekend. Mark which side faces down before you unbolt it. Sharpen at the existing angle and check balance on a nail — an unbalanced blade shakes the whole deck apart over a season.

Plugs are a few dollars and one of the cheapest reliability upgrades there is. Swap it annually and gap it to the spec in your manual. Leave the plug wire disconnected for the rest of the work.

Caked grass under the deck holds moisture against bare metal and rusts it through. Scrape it out with a putty knife and hose it clean, then dry it fully. Paper air filters get replaced; foam filters get washed in soapy water, dried, and lightly re-oiled.

On electric-start or battery mowers, don't store at full or empty charge in a freezing shed. Bring lithium batteries indoors at roughly 40–60% charge. Lead-acid starter batteries should be disconnected and kept on a trickle charger or topped up once mid-winter.

A dry garage or shed beats a tarp on the grass. Keep it level so residual oil doesn't drain into the cylinder, wipe metal surfaces with a light oil rag, and cover it to keep dust and rodents out. Never store a fueled mower next to a water heater or furnace pilot.

The whole point of winterizing is a mower that starts on the first warm Saturday. Put a reminder on the calendar for early spring: reconnect the plug wire, check oil level, air up the tires, and do a test start before the grass gets ahead of you.

Leaving untreated gas in the tank

Costs a carburetor cleaning or rebuild in spring — often more than the mower is worth on older machines.

Tipping the mower the wrong way

Always tip with the air filter and carburetor side up. Tip the other way and oil floods the cylinder, so it smokes badly at the next start.

Skipping the deck clean

Wet clippings hold moisture against steel for five months. That is how a deck rusts through years early.

Storing a lithium battery at 100%

Long-term full charge in cold degrades cells. Aim for a partial charge and a temperature-stable indoor spot.