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How do you winterize a lawn mower for storage?

Updated August 2026

45 minutes · Easy DIY

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Winterizing a mower is a 45-minute, Easy-DIY routine that hinges on one decision: park it with a dry fuel system, or park it with stabilized fuel, but never with untreated pump gas sitting in the carburetor bowl. Ethanol-blended gasoline starts separating and varnishing in 30 to 60 days, and a gummed carburetor is the most common reason a mower refuses to start in April. The rest of the job (fresh oil, a scraped deck, a sharp blade, a battery on a maintainer) takes another 20 minutes and decides how the machine looks in three seasons.

What you need

Before you start: Gasoline vapor is what ignites, not the liquid. Drain or run the tank down outdoors, keep fuel in an approved container, and stay clear of anything with a standing pilot, including the water heater in the same garage. Pull the spark plug wire before your hands go near the blade or under the deck: one compression stroke can turn the blade far enough to cut you. Let the muffler cool 15 minutes before you tip the machine, and wear gloves.

Steps

  1. Pick the storage method first: run the tank dry, or fill it about 95 percent and dose it with stabilizer at the label rate, roughly 1 ounce per 2.5 gallons.
  2. Run the engine 5 minutes after adding stabilizer so treated fuel reaches the carburetor bowl. On the dry route, run it until it stalls, restart it, and let it die a second time.
  3. Change the oil while the engine is warm and the sludge is still suspended. Drain out the plug or tip the mower toward the fill tube with the air filter pointed up, then refill with the 15 to 20 ounces most walk-behinds take.
  4. Pull the spark plug wire, remove the plug, and look at the tip. Replace a plug with rounded electrodes ($3–6). Before it goes back in, squirt a teaspoon of clean oil in the cylinder and pull the cord twice to coat the bore against rust.
  5. Clean or replace the air filter. A paper element is $5–10 and gets tossed once it is gray; a foam element gets washed in soapy water, dried, and re-oiled with a few drops of engine oil.
  6. Tip the mower again, filter side up, and scrape the deck underside until the packed clippings are gone. Wet clippings hold moisture against steel all winter and rot decks from the inside.
  7. Sharpen or swap the blade now instead of in spring, so the first cut of the season is a clean one rather than a shredded one.
  8. Pull the battery on a riding or electric-start mower, store it above 40 degrees, and put it on a maintenance charger. A lead-acid battery left flat all winter rarely comes back, and a replacement runs $60–120.
  9. Store the mower dry and off bare concrete, fuel cap tight, away from any water heater or furnace with a standing pilot. Cover it loosely so condensation can escape.

Or hire it out

A small-engine shop charges $80–150 for a fall service (oil, plug, air filter, blade sharpening, stabilized fuel), plus $60–100 more to tear down and clean a carburetor that gummed up over an untreated winter. The DIY version costs a $6 bottle of stabilizer and a quart of oil.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for mower winterizing sets itself.

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Frequently asked questions

Is it better to store the mower dry or with stabilized fuel?

Both work; pick one and commit. Stabilized fuel keeps the carburetor gaskets and primer diaphragm wet, which matters on newer engines where those are $40–80 parts. Running dry leaves nothing behind to varnish, the safer bet for a machine you will ignore for 6 months. What kills carburetors is the middle path: half a tank of untreated gas evaporating into a sticky film from October to May.

How long does fuel stabilizer actually protect gas?

Bottles claim 12 to 24 months, and that holds only if you treat fresh fuel. Stabilizer cannot rescue gas that already sat a season, so buy the fuel the same week you treat it. Ethanol-free gas, sold at marinas and some stations for about $1 more per gallon, buys extra margin. One $6 bottle covers a full season for a mower.

Do I need to change the oil in fall, or can it wait until spring?

Fall. Used oil carries combustion acids and water, and 5 months of that sitting on the bearings and cylinder wall is what shortens an engine that otherwise runs 10 years. Draining it warm also carries more of the sludge out with it. Most walk-behind engines take 15 to 20 ounces, so a single quart covers the change. The interval by engine hours is on how often to change lawn mower oil.

The mower still will not start in spring. Where do I look first?

Work in order: fuel, spark, then the carburetor bowl. Dump anything older than 60 days and refill with fresh gas. Pull the plug and check for a strong blue spark against the block, and swap it if the tip is fouled ($3–6). If the engine fires on starting fluid and dies, the bowl and main jet are varnished. A bowl-off cleaning is a 45-minute DIY job or $60–100 at a shop.

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