Winterizing a lawn mower means treating or removing the fuel, changing the oil, cleaning the deck, sharpening or pulling the blade, and disconnecting the battery before the machine sits idle for the winter. Skip any one of those steps and you're looking at a gummed-up carburetor, a dead battery, or a rusted deck when you pull it out in spring 2026.
TL;DR
- Run the tank dry or add stabilizer, change the oil, and disconnect the battery before storage.
- Untreated ethanol gas starts breaking down in roughly 30 days and clogs carburetors by spring.
- Zero-turn and stand-on mowers need the same fuel and oil steps, plus a deck rinse and blade check.
- Winterizing a lawn mower properly takes under an hour and prevents most spring no-start calls.
- Robotic mowers like the STIHL iMOW skip fuel steps entirely but still need battery care.
Winterizing benchmarks
30 days
Untreated gas starts degrading
40°F
Below this, 10W-30 oil thickens
50 hours
Typical oil change interval
Why this matters
A mower that sits all winter with old gas in the tank is the number one reason repair shops get flooded every March. Ethanol-blended gas separates and gums up the carburetor jets, and a battery left connected in a cold garage drains itself flat well before the first mow of 2026.
A qualified technician at Metuchen Mower can run through the full list in under an hour if you'd rather not do it yourself, but every step below is something most homeowners can handle with basic hand tools.
How do you winterize a lawn mower before storage?
Work through these steps in order, whether you're storing a push mower, a zero-turn, or a stand-on unit:
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Run the tank dry or add fuel stabilizer. Either burn off the remaining gas by running the engine until it stalls, or top off the tank and add stabilizer at the label's ratio, then run the engine 5 minutes so treated fuel reaches the carburetor.
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Change the oil while the engine is still warm. Warm oil drains faster and carries more of the season's grit and metal particles out with it.
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Pull the spark plug and check the gap. Most small-engine plugs run a 0.030-inch gap; replace a fouled or worn plug now instead of guessing in spring.
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Clean the underside of the deck. Dried grass clippings hold moisture against the metal all winter and accelerate rust.
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Sharpen or replace the blade. A dull blade tears grass instead of cutting it, and starting the season with a sharp edge saves a trip to the shop in April.
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Disconnect or remove the battery. Store it in a dry space above freezing, ideally on a trickle charger or maintainer.
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Store the mower off bare concrete. A pallet, mat, or shelf keeps moisture from wicking up into the deck and tires.
Winterizing a gas walk-behind mower
Walk-behind mowers are the simplest case: fuel treatment, an oil change, a blade check, and a wipe-down cover it. If the mower has a Briggs & Stratton or Honda engine, check the owner's manual for the recommended oil weight before winter, since some engines call for a lighter viscosity in cold storage than they use during mowing season.
Don't forget the air filter. A foam or paper filter clogged with dust from the last mow of the season restricts airflow all winter and makes for a rough first start.
Winterizing a zero-turn or stand-on mower
Zero-turn and stand-on mowers carry more moving parts, so the list gets one item longer: grease the front caster wheels and spindle zerks before storage, since dried-out grease points are a common source of squeaks and premature wear come spring. The fuel and oil steps are identical to a walk-behind, just scaled up for a bigger tank and a V-twin engine.
Homeowners with sloped or hilly properties often run heavier-duty machines, and zero-turn mowers built for hilly acreage tend to have larger fuel systems that benefit even more from stabilizer, since a bigger tank of untreated gas has more surface area to degrade over a New Jersey winter.
Check tire pressure before storage too. A zero-turn or stand-on unit left on soft tires all winter can develop flat spots that never fully round out.
Winterizing a robotic mower
Robotic mowers like the STIHL iMOW skip the fuel and oil steps entirely, but the battery still needs attention. Bring the charging dock and battery indoors if freezing temperatures are expected, and store the battery at a partial charge rather than fully drained or fully topped off, since lithium-ion cells degrade faster at either extreme over a long storage period.
Clean the cutting blades and the underside of the housing before storage the same way you would on a traditional deck. Dirt and grass buildup causes the same rust problems on a robotic mower as it does on a walk-behind.
“If gas sits untreated past 30 days, plan on a carburetor cleaning before the first mow of the season.”
Why winterization steps vary
Not every mower needs the identical checklist. A few things change the exact steps and how much time they take:
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Engine type — 2-stroke and 4-stroke engines have different oil and fuel-mix requirements.
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Fuel type — ethanol-blended gas degrades faster than non-ethanol, so stabilizer matters more with E10.
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Battery type — lead-acid batteries need a maintainer; lithium-ion packs just need a partial charge and a dry, temperate spot.
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Storage location — an unheated shed sees wider temperature swings than an attached garage, which affects both fuel and battery life.
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How the mower was used all season — commercial-duty machines that ran near their engine hour limits need a closer inspection before they sit idle.
What else to prep before winter hits
Winterizing the mower is usually one item on a longer list. If you're already walking the property checking hoses and shutting down irrigation, tackling how to winterize outdoor spigots at the same time prevents a burst pipe from being the thing that ruins spring 2026, not just a stuck mower engine.
It's also a good time to pull other gas-powered equipment — trimmers, blowers, chainsaws — off the shelf and run the same fuel and oil checks, since anything with a small engine and a fuel tank faces the identical ethanol breakdown problem over a New Jersey winter.
Do you need to winterize a mower if you use it in winter too?
No, if you're still running the mower regularly through winter for cleanup or a warm-climate lawn, skip full winterization and just keep the fuel fresh and the blade sharp. Full winterization only makes sense once the mower is going into storage for an extended stretch with no planned use.
How long can fuel sit in a mower before it goes bad?
Untreated ethanol-blended gas starts degrading in about 30 days, forming varnish deposits that clog small carburetor passages. Adding a fuel stabilizer at the correct ratio before storage extends that window through an entire winter, which is why stabilizing the tank is step one on almost every winterization checklist.
Should you winterize a mower before or after the last mow of the season?
Winterize right after the last mow while the engine oil is still warm and easy to drain. Waiting weeks after the final cut means draining cold, thicker oil and gives grass clippings more time to dry and harden onto the deck.
FAQ
How do I winterize a lawn mower before storage?
Run the tank dry or treat the fuel with stabilizer, change the oil while it's warm, clean the deck, sharpen or replace the blade, and disconnect the battery. Store the mower off bare concrete in a dry space.
Do I need to add fuel stabilizer if I run the tank dry?
No, running the engine until it stalls empties the carburetor and fuel lines, which does the same job as stabilizer for most homeowners storing a mower over one winter.
Should I remove the mower battery for winter?
Yes, disconnect the battery and store it indoors above freezing, ideally on a trickle charger, since a cold garage will drain a connected battery flat by spring 2026.
Can I skip changing the oil before winter storage?
You can, but old oil holds moisture and combustion byproducts that sit against internal engine parts all winter, so most manufacturers recommend an oil change before storage rather than after.
Does a zero-turn mower need different winterizing steps than a push mower?
The core steps are the same, but zero-turn and stand-on mowers also need the caster wheels and spindle zerks greased before storage, since those points dry out over a winter of sitting still.
How long does winterizing a lawn mower take?
Most homeowners can winterize a single mower in 30 to 45 minutes, and a technician can typically finish the full checklist in under an hour.
Why won't my mower start in spring after winter storage?
The most common cause is old, untreated gas that gummed up the carburetor, followed closely by a battery that drained flat over the winter months.
Do robotic mowers need winterizing too?
Yes, though robotic mowers skip fuel steps entirely. The battery and charging dock still need to come indoors and the cutting blades need cleaning before the unit sits idle.
One last thing
The detail most people miss isn't the oil or the fuel, it's the tires. Zero-turn and stand-on mowers left all winter on underinflated tires develop flat spots that never fully round back out, which shows up as a subtle vibration the first few mows of 2026. Check pressure before you park it, not after.
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