How to Winterize Your Walk-Behind Lawn Mower

Just two critical steps should protect its inner workings in the off-season

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Lawn mower sitting on a lawn. Photo: iStock

Putting your lawn mower into hibernation till spring? Take a little time now—less than an hour—to winterize it. The bit of effort you spend up front on your walk-behind mower will better ensure that it starts right up for your lawn’s first haircut of 2022, potentially saving you the trouble and expense of a repair.

There are really only two musts. First, you’ll have to clean the deck. Second, you’ll need to stabilize the fuel—or remove the battery, depending on the mower type. Below, the lawn and garden experts at Consumer Reports walk you through how to winterize both gas- and battery-powered walk-behind mowers.

And should you get inspired . . . keep reading! At the end we hit on maintenance next steps that will have your mower humming along at its best when you roll out for that first mow of the year.

Step 1: Clean the Deck

Ideally, you should be in the habit of doing this throughout the season because keeping the blade housing clean helps to ensure optimal mower performance. But the task is essential before winter to prevent moisture in stuck-on grass clippings from causing problems.

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"You want to ensure that neither the underside of your deck nor your blade spends all winter exposed to moisture,” says Misha Kollontai, who leads lawn mower testing for Consumer Reports. “That can lead to corrosion and degrade future performance.”

Because you’ll be working around the mower blade, as a safety measure disconnect the spark plug wire on gas models and remove the battery on battery-powered models. Then turn the mower on its side; with gas models, make sure the air filter is facing up.

A shot under the deck with the garden hose or pressure washer might be enough to remove the clippings, especially if they’re fresh. For dried-on clippings, try a plastic paint scraper or an old bristled pot scrubber; wear heavy work gloves to protect your hands from the blade. If you have silicone spray handy, spray the underside of the deck with it to prevent future buildup.

Store the mower in a dry location. When stowing your mower, try putting a container of mothballs near the deck to prevent mice and other rodents from nesting in the dormant machine. (Mice are notorious for chewing through spark plug wires, fuel hoses, and even pull cords.) Better still, make your garage or storage area inhospitable to rodents in the first place, Kollontai advises. 

“Keep spaces tidy, minimize clutter, ensure that any food is tightly sealed away and inaccessible, and make sure leaves and other organic debris don’t build up around the walls of the structure,” he says. This buildup, he explains, can become a transition point: a covered area where varmints can stay close to walls, and either find or create a way in.

Step 2: Prep the Mower for Storage

For a Gas-Powered Mower: Remove or Stabilize the Fuel
Simply leaving fuel in the tank all winter can wreak havoc on your mower’s engine. Water from condensation can combine with ethanol in the gas, causing clogs, corrosion, and other problems throughout the fuel system. Come springtime, you could be in for a professional carburetor cleaning to the tune of $75 to $100.

If you keep your mower in the basement during the winter, you should remove the fuel regardless of how much is left because storing it inside could be a fire hazard. If there’s only a little fuel left after the last mow of the season, your best bet is to run the tank dry. If the tank is full or nearly full, disconnect the fuel line at the carburetor and drain the remaining gas into a gasoline storage container. (You can add the leftover fuel to your car.)

If you store the mower in a garage or shed, it’s wise to fill the tank with gas and add stabilizer—or even better, use prepackaged gas that has stabilizer already added. (You may find stand-alone stabilizer and gas with added stabilizer at home centers or outdoor power equipment dealers.) For good measure, run the mower for a few minutes so that the stabilized fuel can work its way through the carburetor.

For an Electric Mower: Remove the Battery
Remove the battery or batteries and store them inside your home to minimize temperature fluctuation. Extreme temperatures can shorten the life span of battery cells and cause them to fail prematurely. Most batteries do best when stored between 40° and 80° F. (Check the owner’s manual for the appropriate range for your mower.)

If You Go the Extra Distance

Steps 1 and 2 should keep your mower safe over the winter. But there are a few additional steps you can take now so that you don’t have to worry about them come spring. That includes sharpening your mower blade (as well as any spares you keep on hand). Get step-by-step instructions on how to replace a lawn mower blade when it’s time to get it sharpened.

Not all mowers require oil changes, but if your owner’s manual recommends them, follow through on that advice. Routine oil changes will help extend the life of any engine, as will changing or cleaning the air filter. Spark plugs used to be more of a concern, but their improved technology has reached the point where you need to change the spark plugs only every few years.

Worried your mower might not make it through another season, no matter how diligent you are with the maintenance? Look for end-of-season deals at home centers, using our lawn mower ratings to find models that perform well and to check our exclusive survey data on most and least reliable brands.

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