If you had trouble starting up your lawn mower this spring, it may have had something to do with how you stored it last winter. Even if your mower ran like a champ all summer, you’ll need to prep it for a long period of inactivity. Winterizing your mower now will help guarantee a smooth start next year, and it might just spare you a costly repair. 

Here's how.

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Get the gas out

Over time, gasoline will start to go stale. How long that process takes is the source of some debate, but Briggs & Stratton, a large producer of gas-powered mower engines, says it can occur in as little as 30 days. The Environmental Protection Agency (EPA) says stale gas reacts with air and moisture, forming gums and deposits that can make your mower difficult or impossible to start next spring.

The EPA suggests removing old gas from the tank using a siphon, then running your mower in a well-ventilated area to burn up any remaining fuel. The siphoned gas can be stored in a container (use a UL-approved container, according to the University of Tennessee) with fuel stabilizer over the winter or better still, transferred into to your's gas car. 

If you’re uneasy about the thought of draining gas from the tank, the EPA suggests filling your tank with fresh gas and adding a fuel stabilizer, which prevents the gas from going stale while it’s stored. If you go this route, Briggs & Stratton suggests you power up the mower and let it run for about 10 minutes before storing, which gives the fresh gas and fuel stabilizer enough time to work their way through the fuel system.

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Change the oil

If you didn’t change the oil in your riding mower this season, fall is the perfect time to tackle the chore. Unlike gasoline, oil doesn’t really go bad from prolonged storage, but it does break down and become less effective. The EPA advises routine oil changes for your mower to keep it operating at peak efficiency, which also helps cut emissions.

To tackle this job, park the mower on a level surface. Cud Cadet, a large manufacturer of gas mowers, advises letting the engine cool fully, then disconnecting the spark plug ignition wire to prevent accidentally starting the mower while you work. Remove the oil dipstick and use a siphon to transfer the old oil into a clean plastic container with a tight lid. (Never store used oil in a container that once held chemicals, food or beverages, the EPA advises.) You also could place a drip pan beneath your mower’s oil pan and turn the drain plug. Once the oil is removed, unscrew the oil filter and replace it, running a dab of clean oil around the gasket of the new filter before attaching it. Fill the engine with the oil specified in your owner’s manual, re-inserting the dipstick periodically to check the fill level.

The EPA advises bringing used oil to a service station for recycling. 

While it’s fine to store your mower without oil over the winter, if you forget to add oil before firing up the engine next spring, you could do serious damage.

Replace the fuel filter

In an effort to cut emissions from gasoline, the EPA has gradually required most gas producers to blend gasoline with ethanol, a renewable plant-based fuel typically made from corn. While most cars can operate fine on gasoline blends containing as much as 15 percent ethanol, small gas motors like the one in your mower are notoriously sensitive to its effects. Ethanol has the tendency to produce a gunky buildup in small engines, leading to stalls, poor performance or even failure of the engine. Swapping out your mower’s fuel filter each fall will help capture some of that debris before it makes its way into the engine.

To change the filter, Briggs & Stratton advises clamping the fuel line that leads into the filter to prevent gas from spilling, then using pliers to remove the clamps that secure the filter in place. Replace the filter with the model specified in your owner’s manual, making sure to align the arrow on the filter with the direction fuel travels in your mower, then re-install the clamps. Remove the clamp from the fuel line and fire up the mower briefly to check for leaks.

Switch out the spark plug

A full season of frequent yard cutting can take a toll on your mower’s spark plug, and unlike a car, which typically has four to eight of them, most mowers rely on a single plug. Inspecting or changing the plug now will allow for a smooth start next season.

To start, John Deere, another large manufacturer of gas-powered mowers, advises parking your mower on a level surface. If you have a riding mower, remove the key to prevent accidentally starting the mower, which could cause a nasty shock while you’re working on the spark plug. Remove the plug wire using a ratchet wrench with a spark plug socket. These are sold at auto parts stores and lawn and garden stores. Inspect the plug for cracks, and look at the tip of the plug to see if black carbon deposits have formed. If they haven’t, it’s fine to re-install the plug; otherwise, buy the replacement plug specified in your owner’s manual. Use a spark plug gap gauge (a quarter-sized metal disc frequently sold with spark plugs) to check the gap on the electrode of your new spark plug. Use the gauge to bend back the electrode to the gap specified in your owner’s manual. Re-install the new plug and press the plug wire in place.

Charge and store the battery (riding mowers only)

Even if your battery survived a barrage of wet grass clippings and yard debris this year, it may have some terminal corrosion that will worsen with prolonged storage. Tractor Supply Company, one of the largest retailers of lawn mowers, advises removing the battery and taking it to a dealership or service center for charging.

To remove the battery, Briggs & Stratton suggests removing the cables with a small ratchet wrench, starting with the negative side. Once the battery is disconnected, wipe off the terminals and use a wire brush with special terminal cleaner to polish any exposed metal.

When the battery is cleaned and charged, store it in a cool dry place, keeping it away from heat-producing appliances like a furnace or water heater, as well as from stored containers of gasoline or oil. 

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