How Do I Store My Lawn Mower for the Winter?

A lawn mower that refuses to start in April was almost certainly fine in October — it just sat all winter with old gas gumming up the carburetor, moisture rusting the deck, and a battery slowly dying in the cold. Winterizing a mower takes about an hour, costs almost nothing, and is the difference between a mower that fires on the first pull in spring and one that needs a $75 carburetor cleaning. Do it once, the right way, right after your last mow of the season.

The order matters less than completing every step: fuel, oil, cleaning, blade, filters and plug, battery, and storage. Work through them in whatever sequence suits your mower — gas walk-behind, riding mower, or battery electric — skipping the steps that do not apply to your machine.

Fuel: stabilizer vs. running dry

This is the single most important step, and the one most people skip. Modern gasoline — especially ethanol blends — starts breaking down in as little as 30 days. By spring, untreated gas left in the tank and carburetor turns into varnish and gum that clogs the tiny jets and passages a small engine needs to run. A gummed carburetor is the number one cause of spring no-starts.

Option A: fuel stabilizer (easiest). Add stabilizer to the tank at the manufacturer’s dose (about 1 ounce per 2.5 gallons for most brands, roughly $8 to $12 for a bottle that treats many tanks), then run the engine for 5 to 10 minutes so the treated fuel circulates through the entire fuel system — tank, lines, filter, and carburetor. Top off the tank before storage; a full tank leaves less air space for condensation to form water inside. This method is best if you might need the mower for a late fall cleanup, since the machine stays ready to run.

Option B: run it dry. If you prefer no fuel sitting all winter, run the engine until it sputters out, then drain any remaining fuel from the tank and carburetor bowl (most carburetors have a small drain bolt). This method is foolproof against varnish but means refueling and possibly priming in spring. Either method works — what does not work is leaving untreated gas sitting for five months.

Change the oil

Old oil contains acids and combustion contaminants that corrode internal engine parts during months of sitting. Changing the oil before storage means the engine sleeps in clean lubricant.

Warm the engine for a few minutes first — warm oil drains faster and carries more contaminants out. Tilt or position the mower so the drain plug (or the fill tube, on mowers without a plug) is at the low point, drain into a pan, and refill with the weight your manual specifies — most walk-behind mowers take SAE 30 or 10W-30, about 15 to 20 ounces. Do not overfill; check the dipstick. Take the used oil to any auto parts store for free recycling.

While you are at it, this is the ideal moment for the annual oil change anyway. Doing it now instead of spring means one less spring chore and a protected engine all winter.

Blade sharpening and deck cleaning

Clean the deck thoroughly. Disconnect the spark plug wire first — this is non-negotiable whenever your hands go near the blade. Tip the mower on its side with the air filter and carburetor facing up (tipping the wrong way floods them with oil), and scrape the caked grass from under the deck with a putty knife or plastic scraper. Dried grass holds moisture against the steel all winter and starts rust. Wash with a hose if needed, then let it dry completely. A light spray of silicone lubricant under the deck discourages future buildup and resists rust.

Sharpen or replace the blade. A sharp blade cuts cleanly; a dull one tears grass and invites disease. Remove the blade (brace it with a block of wood, loosen the bolt — note that some bolts are reverse-thread), and sharpen with a file or bench grinder, keeping the original bevel angle. Balance matters: hang the blade on a nail through the center hole — if one side dips, grind a little more off the heavy side. An unbalanced blade vibrates and wears bearings. Replacement blades run $15 to $30 if yours is nicked, bent, or sharpened down to a stub.

Inspect the belts on riding mowers while the deck is accessible. A frayed or cracked belt is a spring breakdown waiting to happen; replacing it now ($20 to $50) beats a mid-season failure.

Air filter and spark plug

Air filter. A clogged filter chokes the engine and wastes fuel. Paper filters ($8 to $15) should be replaced annually — tap out loose dirt as a stopgap, but replace rather than wash paper elements. Foam filters can be washed in warm soapy water, dried completely, and lightly re-oiled. If the filter is oil-soaked or crumbling, it is overdue.

Spark plug. Pull the plug and inspect it. A light tan or gray insulator means healthy combustion; heavy black carbon, oil fouling, or a worn, rounded electrode means replace it ($4 to $8). Even a decent-looking plug is cheap insurance to replace once a year — it is the easiest starting improvement you can buy. Gap the new plug to your manual’s spec (usually 0.030 inches) with a gap tool, and do not overtighten — snug plus a quarter turn on a used head is plenty.

Battery care (riding mowers and electric starts)

Batteries self-discharge over winter, and a battery that freezes while discharged can be permanently damaged. Cold does not just make starting harder — it can kill a neglected battery outright.

Remove the battery and store it somewhere dry where temperatures stay above freezing — a basement shelf or heated garage corner is ideal, not the unheated shed. Clean the terminals with a wire brush and a baking-soda-and-water paste, then coat them lightly with dielectric grease or petroleum jelly to prevent corrosion.

Keep it charged. A battery maintainer/trickle charger ($25 to $45) is the gold standard: connect it and forget it all winter. Without one, charge the battery with a regular charger every 4 to 6 weeks. A battery left dead all winter often will not come back in spring, and replacements run $40 to $100.

Battery-electric mowers. Remove the lithium-ion battery packs and store them indoors at room temperature, ideally at around 40 to 70 percent charge — not fully charged, not dead. Check them every couple of months; top up if they have dropped significantly. Never store lithium batteries in freezing conditions or on a charger all winter.

Storage location and covering

Where. The ideal spot is dry, enclosed, and out of temperature extremes — a garage or shed beats an open carport, which beats a tarp in the yard. Keep the mower off bare dirt or concrete if possible; a wood pallet or rubber mat underneath reduces moisture wicking into the deck. Keep gas mowers away from furnaces, water heaters, or any ignition source — fuel vapors are the concern, even with stabilized fuel.

How to position it. Store walk-behind mowers on all four wheels, normal orientation. Do not hang them on a wall by the handle or stand them on end for months — oil migrates where it should not. For riding mowers, park with the parking brake off if the floor is level (set brakes can seize) and chock the wheels instead. Slightly overinflate the tires (a few PSI above normal) since they will lose pressure over winter.

Cover it. A breathable mower cover ($20 to $40) keeps dust off while letting moisture escape. Avoid wrapping in airtight plastic sheeting — trapped condensation rusts faster than open air. If mice are a concern in your storage area, stuff steel wool in the exhaust and air intake openings and place mothballs or peppermint-oil sachets nearby; rodents nesting in an air filter box is a classic spring surprise.

What this costs

Total DIY winterization cost: roughly $20 to $40 in supplies you probably already half own.

Mistakes to avoid

• Leaving untreated gas in the tank. The number one spring no-start cause. Stabilize it or drain it — there is no third option that works.
• Tipping the mower carburetor-side down. Oil floods the air filter and carburetor. Always tip with the filter and carburetor facing up.
• Working near the blade with the plug connected. Disconnect the spark plug wire before touching the blade or deck. A bumped blade can turn the engine over.
• Storing the battery in the freezing shed. A discharged battery can freeze and die permanently. Bring it inside and keep it charged.
• Wrapping the mower in airtight plastic. Trapped moisture rusts steel faster than open air. Use a breathable cover or nothing.
• Skipping the deck cleaning. Caked grass holds moisture against the deck all winter and starts rust you will find in spring.
• Forgetting where you put the drain bolt or blade bolt. Put small parts in a labeled bag taped to the handle. Future you will be grateful.

Frequently asked questions

Should I drain the gas or use stabilizer? Either works if done properly. Stabilizer is easier — add it, run the engine 5 to 10 minutes to circulate treated fuel everywhere, top off the tank, and you are done. Draining is more thorough but requires draining the carburetor bowl too, not just the tank. The only wrong answer is doing nothing.

Can I leave the battery in the mower over winter? You can, but you will probably regret it. Batteries self-discharge, and a dead battery in freezing temperatures can freeze and suffer permanent damage. Remove it, store it above freezing, and keep it on a maintainer or charge it every month or so.

Do I need to change the oil before storage, or can it wait until spring? Before storage. Used oil contains acidic combustion byproducts that corrode internal parts during months of sitting. Fresh oil protects the engine all winter, and it is one less job in spring.

Is it okay to store my mower outside under a tarp? It is better than nothing, but it is the worst acceptable option. Tarps trap moisture underneath, temperature swings cause condensation, and UV degrades plastic parts. A garage or shed is far better; if outside is truly the only option, elevate the mower on a pallet and use a breathable cover rather than a plastic tarp.

My mower is electric/battery-powered. What do I skip? Skip everything fuel and oil related — no stabilizer, no oil change, no spark plug, no air filter (most electrics have none). You still clean the deck, sharpen the blade, and store it dry. The critical step is the battery: remove lithium packs, store indoors at room temperature at partial charge, and check them every couple of months.

When to call a pro

Most winterization is straightforward DIY, but call a small-engine repair shop if the mower already will not start (a gummed carburetor rebuild runs $75 to $150), if a riding mower needs belt or transmission work you are not comfortable with, or if the engine has low compression, smokes heavily, or makes knocking noises — those are internal problems, not storage prep. Also consider a professional tune-up ($75 to $150) every few years even with good DIY maintenance; a pro will catch worn cables, weak ignition coils, and governor issues you might miss. But for the annual winter put-away itself — fuel, oil, blade, battery, and a dry spot — you have everything you need right here.