How to Winterize a Lawn Mower (So It Starts First Pull in Spring)
Winterize your lawn mower in about 30 minutes: stabilize the fuel, change the oil, clean the deck, and store it dry so it starts first pull next spring.
- Difficulty
- Beginner-friendly
- Time
- 30–45 minutes
- Est. cost
- $10–$30 (fuel stabilizer, oil, spark plug)
- Season
- fall
By Keepstead Editorial Team · Published October 28, 2026 · 5 min read
Last reviewed October 28, 2026
Quick answer
Winterize a gas mower in about 30 minutes: treat or drain the fuel, change the oil, clean the deck, service the air filter and spark plug, fog the cylinder, and store it dry indoors. Skipping this is the top reason mowers refuse to start in spring — stale fuel alone gums up the carburetor in as little as 30 days.
A mower that ran fine on its last fall cut can refuse to start in April, and the culprit is almost always winter storage, not a broken engine. Untreated gasoline goes stale, old oil turns corrosive, and grass caked on the deck holds moisture against steel all winter. Half an hour of care now buys you a first-pull start in spring.
Tools needed
- Wrench or socket set for the drain plug
- Oil drain pan and funnel
- Plastic scraper for the deck
- Fuel stabilizer
- Fresh engine oil (grade per your manual)
- New spark plug
- Clean rags
- Work gloves and eye protection
Step-by-step: winterize your mower
Step-by-step instructions
Deal with the fuel first
You have two good options. Option one: on your last mow of the season, run the tank dry and let the engine stall, which empties the carburetor. Option two: fill the tank nearly full, add fuel stabilizer at the dose printed on the bottle, and run the engine for 5–10 minutes so treated fuel circulates through the whole fuel system. A full tank also limits condensation inside the tank over winter. What you must not do is park it with a half tank of untreated fuel.
Change the oil while the engine is warm
Warm oil drains faster and carries more contaminants out. Run the engine for a few minutes, shut it off, disconnect the spark plug wire, and drain the oil into a pan through the drain plug or by tipping (air filter side up). Refill with the oil grade your manual specifies and check the dipstick — overfilling is as harmful as running low. Take the used oil to a recycling point; never pour it on the ground or down a drain.
Clean the deck thoroughly
Caked grass holds moisture against the deck all winter and invites rust. With the spark plug wire disconnected and the air filter side up, scrape the underside of the deck with a plastic scraper (metal gouges the finish), then brush it out and wipe it dry. While you are there, inspect the blade: nicks and dull edges are worth sharpening or replacing now, not on the first mow of spring.
Service the air filter and spark plug
Remove the air filter cover and tap a paper filter clean, or replace it if it is torn, oil-soaked, or grey with dust. A foam filter can be washed and re-oiled per the manual. Then pull the spark plug, check the electrode for carbon buildup or wear, and replace it if it looks fouled — a fresh plug is cheap insurance for a spring start.
Fog the cylinder
With the spark plug out, add about a teaspoon of fresh engine oil or a short spray of fogging oil into the cylinder. Pull the starter cord slowly a few times to spread the oil over the cylinder walls, which prevents rust on bare metal during months of sitting. Refit the spark plug loosely, and leave the spark plug wire disconnected until spring.
Store it dry, level, and covered
Park the mower on a level surface in a dry garage or shed, fuel cap tight, with a breathable cover over it. Keep it away from snowmelt puddles and out of the path of salt spray. If your mower has a battery (electric start), remove it and store it indoors at room temperature. Finally, note the date and the oil grade on a tag on the handle — future-you will be grateful in April.
What if you forgot to winterize?
If spring arrives and the mower will not start, work through this order: fresh fuel first (drain the old tank completely), then a new spark plug, then a clean air filter. If it still will not start, the carburetor is likely varnished from stale fuel and needs cleaning — a common shop job, but an avoidable one next year.
| Symptom in spring | Likely cause | Fix |
|---|---|---|
| Pulls but never fires | Stale fuel or fouled plug | Drain tank, refill with fresh fuel, replace plug |
| Starts then stalls | Clogged carburetor jet or dirty filter | Clean filter; carburetor cleaning if it persists |
| Smokes heavily at startup | Oil in the cylinder from tipping | Let it burn off briefly; check oil level |
| Blade vibration | Bent or unbalanced blade | Replace the blade; do not mow with a bent blade |
A 30-minute habit that pays every spring
Pair mower winterizing with your other fall shutdown tasks — draining outdoor faucets and stowing hoses — and it becomes one Saturday chore instead of a spring repair bill. Your reward is a mower that starts on the first pull while the neighbours are still troubleshooting theirs.
Frequently asked questions
- Should I drain the gas or use fuel stabilizer for winter storage?
- Either method works if done properly. Draining the tank and running the carburetor dry removes all stale-fuel risk, while stabilizer-treated fuel protects the system for 12–24 months depending on the product. The mistake to avoid is leaving untreated fuel in the tank all winter: it goes stale in as little as 30 days and gums up the carburetor.
- Do I really need to change the oil before winter?
- Yes, and before storage is the right time. Used oil carries acids and combustion byproducts that corrode internal parts while the mower sits idle. Fresh oil coats the engine with clean lubricant, so spring startup is gentler on the engine.
- Why does my mower not start in spring even though it ran fine in fall?
- Stale fuel is the most common cause, followed by a fouled spark plug and a clogged air filter. If the mower sat with untreated fuel, the carburetor jets may be varnished shut and need cleaning or a rebuild. Winterizing each fall prevents most of these no-start cases.
- Can I store my mower outside under a tarp for winter?
- It is not recommended. Tarps trap moisture against the deck and engine, which accelerates rust, and freeze-thaw cycles can crack plastic parts. A dry garage or shed is far better. If outdoor storage is unavoidable, use a breathable mower cover, raise the mower off the ground, and keep it out of standing water.
- Should I remove the battery from a battery-powered mower for winter?
- Yes. Remove the battery, charge it to roughly half to three-quarters full, and store it indoors at room temperature away from freezing conditions. Lithium batteries lose capacity faster when stored fully charged or fully empty in a cold garage, and most manufacturers recommend against charging a frozen battery.
Sources & references
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This guide is for general informational purposes. Conditions vary by home, local codes, and equipment. See our disclaimer.