How to Winterize a Lawn Mower: Gas or Robot

Winterizing a lawn mower depends on the type you have. A gas mower needs its fuel drained or stabilized before it sits all winter, while a robot mower needs to come indoors to protect its battery from the cold.

Learning how to winterize a lawn mower the right way means paying attention to timing and routine. In this guide, we break down the exact steps for each type, plus how to store and restart your mower once the season turns.

Do Lawn Mowers Need to Be Winterized?

Yes, every mower requires some form of winterizing, though the specifics depend on its power source. Here's how gas and robot mowers compare.

When to Winterize a Lawn Mower

You should winterize your lawn mower right after your final mow of the season, before the first hard frost. This is usually when grass growth stops, which gives you a few weeks to prepare your lawn mower for the season ahead.

For a gas mower, the countdown starts at your last fill-up. Untreated fuel only stays good for about a month once it's sitting in the tank, so if you fill up in early October, it's already oxidizing well before any freeze shows up.

If you're still using your lawn mower through the colder months, you can skip the fuel step altogether, since regular use keeps the tank cycling with fresh gas.

None of this applies to a robot mower, since it doesn't run on fuel or oil.

Our guide on when to stop mowing your lawn covers the temperature and growth signs that tell you it's time for that last cut, and the right height to leave it going into winter.

How to Winterize a Gas Lawn Mower

The most crucial step in winterizing a gas lawn mower is addressing the fuel. After that, change the oil and clean the deck.

1. Drain the fuel or stabilize it

   Left untreated, gas breaks down and can corrode and clog the fuel system, so drain it if you won't run the mower again until spring, or stabilize it if you might use it before then. Never do both at the same time.

   • Drain it. Run the mower until the tank is completely empty or the engine dies on its own. This clears all the liquid out of the fuel lines and carburetor. It's also the safer choice if your mower lives in an attached garage or basement, since leftover fuel can be a fire risk.
   • Stabilize it. Add a fuel stabilizer to fresh gasoline, then fill the tank almost to the top to reduce the air space where condensation forms. Run the engine for ten minutes so the treated fuel reaches the carburetor.

2. Change the engine oil

   Warm the engine up first so the old oil drains out cleanly, then refill with the oil type listed in your owner's manual. Used engine oil holds acidic byproducts left over from combustion, and those sit against the engine's internal surfaces for months if left in over winter. This step isn't mandatory the way the fuel step is, but it's worth doing to help the engine last longer.

3. Clean the deck and sharpen the blade

   Hose down the underside of the deck, clearing packed grass and dirt, using a scraper on anything dried on. Damp clippings hold moisture against bare metal for months, and can cause rust. Check the air filter for loose debris while you're in there too, and replace it if it is heavily soiled or damaged.

   Sharpen or replace the blade while the mower's already apart, so spring turns into a fuel-and-go job instead of a separate trip to the shed to deal with a dull blade. A dull blade tears at grass, leaving its tips ragged and brown.

   For the correct filing angle, or to check whether your blade needs sharpening or replacing, see our guide on how to sharpen a lawn mower blade.

How to Winterize a Robot Lawn Mower

Winterizing a robot mower takes four steps, and the battery is the one thing that needs protecting from a hard winter, even on a mower built to handle months of rain.

1. Charge it, then power it down

   Place the mower on its charging dock and let it fully charge before switching it off. Turn the main power off completely, so the battery doesn't drain slowly while it sits unused all winter. Pause any automatic mowing schedules before storing it.

2. Deep clean it

   Turn the mower over and scrape off any packed grass and mud from the deck and wheels. A plastic or wooden scraper works better than metal here. Wipe down the sensors and outer casing with a damp cloth, then use a stiff brush on anything more stubborn. A blast of compressed air clears out whatever's stuck in the vents and crevices, where a cloth can't reach.

   If your mower has an IPX6 water-resistance rating or higher, you can do a quick rinse instead of a full scrub.

3. Cover the sensor before storage

   A robot mower with an exposed navigation sensor needs its protective cover fitted before storing it. The Dreame A3 AWD Pro Series uses a 3D LiDAR sensor to map the yard and must have the dedicated protective cover fitted before storage.

   Rest the mower flat on the floor, or on a stand if it has one, then cover it lightly with a breathable cloth to keep dust off without trapping moisture.

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4. Store the charging station properly

   Disconnect the charging station's power supply and bring it into a dry, frost-free garage or shed. Keep it off bare concrete if you can; the same moisture risk that affects the mower applies to the station's electronics too.

Where to Store a Lawn Mower Over Winter

Store a lawn mower indoors in a dry, protected location like a garage or garden shed to shield it from harsh weather. A cover isn't required indoors, but if you use one, dry the mower completely first. A damp mower creates condensation under a cover, which can damage mechanical and structural parts.

Staying dry matters more than staying warm, so an unheated space works fine as long as it stays dry. A few other habits keep it in good shape through the season.

• Use cardboard or plywood. Never place it directly on bare concrete. Concrete draws moisture upward from the ground, and prolonged contact can rust the mower's underside even in a space that feels dry.
• Clear the area first. Remove food sources nearby and any grass debris. Leftover food and debris attract pests, and once inside, they chew through wiring and air filters.
• Check on it mid-winter. This catches hidden problems early, before they turn into permanent damage or an expensive repair.

Getting Your Mower Running Again in Spring

Getting a well-winterized mower running again just means undoing what you did in fall. For a gas mower:

1. Add fresh fuel if the tank was left dry.
2. Reconnect the spark plug you pulled before winter.
3. Check the oil level and top it off if it's low.
4. Check the tire pressure and add air if it's needed.

If it still won't start after all that, the fuel left in it over winter is almost always the reason.

A robot mower takes fewer steps to bring back online.

1. Set the mower on its charging station and let it charge fully.
2. Put the charging station back in its original spot if you moved it for storage. If your yard changed significantly over winter, it's worth remapping so the mower learns the new layout.
3. Remove any protective sensor cover before the mower's first run.

A running mower doesn't mean it's time to start cutting. Our guide on when to mow your lawn in spring covers the grass-height and soil signs to watch for, including how the one-third rule protects that first cut.

Winterizing keeps your lawn mower ready to go

Both gas and robotic mowers require specific winterizing routines, but taking the time to prepare them properly can make a significant difference come spring. If you do it right, your mower will start up easily when the new season begins, ready to give your lawn its first cut.

For robot mowers, you don't need to worry about fuel winterization. Browse our range of robot lawn mowers to find the right model for your yard.

Frequently Asked Questions

Is it okay to leave gas in a lawn mower over winter?

Only if it's treated. Untreated fuel starts breaking down in about a month, which can cause the mower to not start in spring. If your tank isn't drained or stabilized yet, the fuel step above walks through both options.

How long does gas last in a lawn mower before it goes bad?

About a month untreated, but longer if you add a stabilizer according to the product label. The leftover gas oxidizes and picks up moisture, which can corrode or clog the fuel system. That's why a tank that's only partly full can cause more trouble than an empty one.

Should you disconnect the battery on a lawn mower in winter?

On a gas mower with a starter battery, remove it entirely instead of disconnecting it. Pull the negative cable first, then bring the battery indoors somewhere it won't freeze. A robot lawn mower's battery isn't removable, so you need to move the whole machine indoors.

Can you leave a lawn mower outside in winter?

No. A cover blocks rain, but it doesn't protect the mower from everything winter brings. Left damp for weeks, metal parts start to rust, and extended cold shortens battery life. Both risks apply to robot mowers rated for wet weather.

Is it better to leave your lawn long or short for winter?

It's generally better to cut your lawn slightly shorter for the final mow before winter. Cutting it too short can damage the grass's root system going into the cold months, while leaving it too long can cause matting under snow.

Do I need to winterize a lawn mower if my winters are mild?

Yes, you still need to prep your lawn mower if your winters are mild. Winterizing has more to do with gas breaking down and gumming up the engine than with freezing temperatures.