Should I Run My Lawn Mower Out of Gas Before Winter

Quick Overview

• Yes, running your lawn mower out of gas before winter is a smart move, but a fuel stabilizer works almost as well with less effort.
• Old gas left sitting all winter can separate and gum up your carburetor by spring.
• Ethanol gas is the main culprit. It pulls in moisture and breaks down faster than pure gasoline.
• Cold garages in Minnesota or Ohio and humid sheds in Georgia both raise the risk, just in different ways.
• My pick: run the tank dry if you have 10 spare minutes, use stabilizer if you don’t.

It was a cold October afternoon in my driveway outside Columbus, Ohio. I remember the smell of cut grass mixing with the first frost in the air. I rolled my Toro mower into the shed, gas tank still half full, and shut the door for the season.

Five months later, that mower would not start. I pulled the cord eight times. Nothing but a weak sputter and the smell of stale gas. That mistake taught me why people ask whether they should run a lawn mower out of gas before winter, and I have tested both sides of that question ever since.

This guide is for anyone with a gas mower sitting in a garage, shed, or carport right now, wondering what to do before the first snow hits. I have run mowers dry, stabilized fuel, and skipped both in different years. I will walk you through what actually works.

Maybe you just bought your first house and this is your first fall with a mower to manage. Or maybe you have owned mowers for years and just never thought hard about what happens inside that tank once the season ends. Either way, this guide covers both situations in plain language.

I am not selling you a product here. I own a Toro, I have borrowed a neighbor’s Honda for testing, and I have tried stabilizer from two different brands over the years. None of them paid me to say anything. I just want you to have a mower that starts on the first pull next spring.

Why Winter Storage Matters More Than You Think

Winter storage matters because gas left sitting for months can wreck your carburetor before spring ever arrives. A mower that sat all winter with old fuel is the number one reason mowers fail to start in March and April.

Most people think of a mower as a simple machine. Pull the cord, it starts, you mow. But gas is not stable forever. It changes chemically the longer it sits, and cold temperatures speed up some of those changes while humidity speeds up others.

Think about a loaf of bread on your counter. Fresh, it is soft and easy to work with. Leave it out for weeks and it turns hard and stale. Gas does something similar, just at a chemical level instead of a physical one. The compounds that make it burn cleanly start to break down the moment it sits still.

A mower engine only needs a small amount of clean fuel flowing through a few tiny passages to run right. Once those passages get coated with gummy residue, even a strong battery or a fresh spark plug will not save you. The carburetor has to be clean for the whole system to work.

What Happens to Gas Left Sitting All Winter

Gas left sitting all winter starts to break down within 30 to 60 days. The lighter compounds that make it easy to ignite evaporate first, leaving behind a thicker, gummier residue.

That residue clogs small fuel passages inside your carburetor. I have taken apart carburetors in the spring and found a sticky, varnish-like coating where clean fuel should have been.

Here is the part that surprised me the first time I saw it. The gas did not look obviously bad. It was still yellow, still liquid. But it smelled sour and stronger than fresh gas, almost like nail polish remover.

Ethanol Gas and Why It’s the Real Problem

Ethanol gas is the real problem behind most winter mower failures. Most gas stations in the US sell E10, which is 10 percent ethanol blended with regular gasoline.

Ethanol is hygroscopic. That means it absorbs water straight out of the air. In a garage in Minnesota, temperature swings between day and night cause condensation inside the tank, and that moisture gets pulled into the fuel.

Once enough water gets in, the ethanol and water separate from the gasoline. This is called phase separation. You end up with a layer of watery ethanol at the bottom of the tank and gas floating on top, and neither one burns clean.

I learned this the hard way in a Georgia shed one humid summer. My trimmer, not even the mower, wouldn’t run right after just a few weeks of ethanol gas sitting untouched. The float bowl had a milky residue in it.

Some gas stations sell ethanol-free fuel, sometimes labeled as recreational fuel or marine fuel. It costs more per gallon, usually 50 cents to a dollar more, but it resists moisture absorption much better. I use it in my chainsaw and trimmer now. For a mower, the cost adds up fast if you fill a full tank each week during peak season, so I stick with regular E10 gas and just manage the storage side carefully instead.

The ignition system on your mower does not care what kind of fuel you use, as long as the fuel actually vaporizes correctly inside the carburetor. Separated ethanol gas creates a weak, inconsistent burn. That is why a mower with bad gas often starts rough, runs uneven, and stalls out instead of failing to start completely.

Running It Dry vs. Using a Fuel Stabilizer

Both methods protect your mower from bad gas, but they do it in different ways. Running the tank dry removes the fuel entirely. Stabilizer keeps the fuel usable by slowing down the chemical breakdown.

Neither method is perfect, and I want to be honest about both before you pick one.

The Case for Running the Tank Empty

Running the tank empty means there is no old gas left to go bad. If the tank and carburetor are dry, ethanol separation and gumming simply cannot happen inside them.

This is the method my grandfather used on his Craftsman mower for 20 years without a single spring start-up problem. Simple, cheap, no additives needed.

The drawback is real, though. Running an engine dry means running it out of fuel while it’s actually working, and that can pull in tiny amounts of debris or air that stresses the fuel pump on some models. It also takes time you have to actually stand there for.

I have talked to a small engine mechanic in my area who services mowers for half the neighborhood every spring. He told me that running dry causes almost no real damage on standard push mowers with simple carburetors. His concern is mostly with fuel-injected mowers, which are less common on residential push mowers but do show up on some higher-end riding mowers and zero-turn models.

If you own a fuel-injected riding mower, check your owner’s manual before running it dry. Some manufacturers specifically recommend against it for those models, since the fuel pump relies on liquid fuel for cooling and lubrication during operation.

The Case for Stabilizer Instead

Fuel stabilizer works by slowing down the oxidation and separation process in stored gas. Brands like Sta-bil and Briggs & Stratton’s own stabilizer claim to keep gas fresh for up to 12 months.

I have used Sta-bil in my Troy-Bilt mower for three winters running, and it started on the second pull each spring. That is a real result, not a guess.

The honest drawback is that stabilizer does not stop ethanol from absorbing moisture. It slows the breakdown of the gasoline itself, but a humid shed can still cause water buildup over a long winter. Stabilizer also costs money every single year, small money, but it adds up.

You also have to measure it correctly. Most stabilizer bottles list a ratio, often around one ounce per gallon of gas. Pour in too little and it barely helps. Pour in too much and you are just wasting product without any added benefit.

I made the mistake once of adding stabilizer to a tank that already had gas from midsummer sitting in it for two months. It did not save that fuel. The carburetor still gummed up slightly by spring, just less than it would have without any stabilizer at all. The lesson stuck with me: stabilizer is a prevention tool, not a fix for gas that already started breaking down.

Which Method Actually Protects Your Engine Better

Running the tank dry protects the carburetor better because there is no fuel left to gum it up at all. Stabilizer protects the fuel supply chain better because it keeps gas usable for spring mowing without an extra trip to the gas station.

If I had to pick one for a mower sitting in a cold Midwest garage all winter, I would run it dry. For a mower in a milder Southern climate that only sits idle for six or eight weeks, stabilizer is plenty.

There is a middle option too, and I use it sometimes when I am short on time. Add stabilizer to the tank, then run the mower for five or ten minutes to circulate the treated fuel through the entire carburetor before storage. This way, even the small leftover fuel in the carburetor bowl has stabilizer in it, not just the fuel sitting in the tank.

This hybrid approach takes a bit more effort than stabilizer alone, but less time than a full dry run. It has worked well for me on years when I had a busy fall and only twenty minutes to spare before the first snow warning came through.

Compression Table: Running Dry vs. Stabilizer

How to Run Your Mower Out of Gas the Right Way

The right way to run your mower out of gas is to let it run on its own until it sputters and stops, rather than trying to drain the tank by hand first. Draining by hand is messy and usually leaves fuel in the carburetor anyway.

Do this outside or in a well-ventilated garage. Gas fumes build up fast in an enclosed shed, and you do not want to breathe that in for 20 minutes.

Pick a calm, dry day if you can. Wind carries the exhaust smell away faster, and you avoid tracking mud or wet leaves back through your garage afterward. I usually do this chore on a Saturday morning in early November, before the first hard freeze hits Ohio.

Keep kids and pets away from the mower while it runs. It sounds obvious, but a running mower with no grass to cut still throws small debris and hot exhaust, and curious dogs love to get too close.

Step-by-Step: Draining the Tank Safely

1. Move the mower outside onto your driveway or a flat patch of concrete.
2. Start the mower like normal and let it idle in place. Do not mow with it.
3. Let it run until it sputters, slows down, and shuts off on its own.
4. Try restarting it once. If it starts again, let it run until it dies for good.
5. Tip the mower slightly (spark plug side up) to check for any remaining fuel pooling in the tank.

I did this in my Ohio driveway last October. The mower ran for about 14 minutes before it started coughing, then died with one last little sputter that almost sounded relieved.

My neighbor does the same thing with his Craftsman, but he mows one final low pass around his yard first to burn off fuel while actually doing something useful. That works too, as long as the mower is not under heavy load when it finally runs dry. A mower struggling to cut thick grass while running low on fuel puts more strain on the engine than one just idling in place.

How Long to Let It Run Before It Stops

Most mowers with a nearly empty tank take 10 to 20 minutes to run completely dry. A tank that still has half a gallon or more can take closer to 30 minutes.

Do not rush this by tipping the mower to drain gas out manually while it is off. That risks spilling fuel on hot engine parts or into the air filter housing.

Watch the engine sound as it gets close to empty. It usually surges slightly first, revving up and down a little as the last bit of fuel sloshes around and stops feeding evenly. Then it slows down, coughs once or twice, and stops. That whole sequence usually takes less than a minute once it starts.

If your mower has a clear or translucent fuel line, you can sometimes see the fuel level dropping and watch for air bubbles right before it stops. Not every model has this, but it is a helpful visual cue if yours does.

What to Do With the Carburetor Afterward

After the tank runs dry, the carburetor bowl usually still has a small amount of fuel left inside it. Some owners drain the carburetor bowl separately using the small drain screw on the bottom.

I do not bother with this step on most mowers. The tiny amount left in the bowl evaporates on its own within a few days if the tank stayed empty. On older Honda engines with a manual fuel shutoff valve, though, closing that valve before the final run helps drain the carburetor more completely.

Here is how that works. Close the fuel shutoff valve first, then start the mower and let it run. It will use up the fuel already in the carburetor bowl and lines instead of pulling more from the tank. This empties the carburetor specifically, which is the part most prone to gumming up.

Not every mower has this valve. Check near where the fuel line leaves the tank. If you see a small lever or knob there, you likely have one. If not, running the tank fully dry the standard way still gets you most of the same benefit.

Mistakes People Make Before Winter Storage

The biggest mistake people make before winter storage is skipping basic maintenance while focusing only on the fuel. Fuel is important, but old oil, a dirty air filter, and a worn spark plug all cause spring starting problems too.

I have made every mistake on this list at least once.

Forgetting the Oil Change

Forgetting the oil change before winter means your mower sits with old, dirty oil circulating through the engine internally all season. Old oil holds moisture and tiny metal particles that settle and cause more friction on that first spring start.

Change the oil in fall, not spring. Fresh oil protects internal parts during the months the engine sits completely still.

Most push mowers hold around 15 to 18 ounces of oil, and a quart bottle from any hardware store covers you with extra to spare. The process takes ten minutes. Warm the engine up for a minute first, then tip the mower on its side, drain the old oil into a pan, and refill with fresh oil to the level marked on the dipstick or fill cap.

I skipped this step for two years running when I first started mowing my own lawn. Nothing catastrophic happened, but the engine on my old Craftsman ran noticeably rougher by the third spring, and a mechanic later told me sludge buildup was likely part of the reason.

Storing It With a Full Tank by Accident

Storing a mower with a full tank by accident happens more than people admit. You top off the tank in September thinking you will mow one more time, then winter shows up early.

A full tank of ethanol gas sitting for five months is about the worst combination possible. There is more fuel to go bad and more surface area for moisture to collect. If this happens to you, run the mower until the tank empties before storage, even if it takes two sessions.

This happened to me two years ago. I filled the tank in late September, thinking one more warm stretch of weather was coming. It never did. A surprise early frost hit Ohio in the first week of October, and the mower sat with a completely full tank until the following March.

That spring, the mower started, but it ran rough for the first ten minutes, coughing and losing power at low throttle. A quick carburetor cleaning fixed it, but it was an avoidable hassle. If you catch yourself in this situation, do not just leave it. Take fifteen minutes on the next mild day to run the tank down.

Skipping the Air Filter and Spark Plug Check

Skipping the air filter and spark plug check before storage leaves your mower vulnerable to a rough start in spring even if the fuel situation is perfect. A dirty air filter restricts airflow, and a worn spark plug weakens the spark needed for ignition.

Pull the spark plug in fall. Look for black, crusty buildup on the tip. If you see it, replace the plug. It costs less than four dollars and takes two minutes.

While you have the plug out, check the air filter too. Foam filters can be washed with mild soap and water, then left to air dry completely before reinstalling. Paper filters just need a light tap to knock loose debris out, or a full replacement if they look gray and clogged.

I check both every fall now, right after I run the tank dry. It only adds five minutes to the whole process, and it means the mower is genuinely ready to go come spring, not just fueled correctly but mechanically sound too.

Compression Table: Common Storage Mistakes and Fixes

How Climate Affects Winter Storage

Climate affects winter storage because cold, humid, and mild conditions each stress a mower’s fuel and metal parts differently. A Minnesota garage and a Georgia shed create two completely different sets of problems for the same mower.

I have stored mowers in three different climate zones, and each one taught me something different.

Cold Garages in the Midwest and Northeast

Cold garages in the Midwest and Northeast cause big temperature swings between day and night, and that swing creates condensation inside the fuel tank. That moisture feeds ethanol separation faster than steady cold alone would.

In my Ohio garage, temperatures swung from 40 degrees in the afternoon sun to well below freezing at night in December. That daily swing is what really damages stored fuel, more than the raw cold itself.

A friend in Minneapolis keeps his mower in an unheated detached garage, and he told me the swings there are even more extreme, sometimes 50 degrees between a sunny afternoon and an overnight low. He runs his mower dry every single fall now, no exceptions, because he learned the same lesson I did after a rough spring start-up a few years back.

If your garage sits attached to your house, you likely have less temperature swing than a detached shed or garage exposed to full sun and open air. That slightly reduces the risk, but it does not eliminate it. Ethanol still pulls in moisture from normal humidity in the air, swing or no swing.

Mild Winters in the South and Southwest

Mild winters in the South and Southwest put less stress on stored fuel because temperature swings are smaller and the mower often gets used again within a few weeks. A mower in Arizona might sit idle for six weeks instead of five months.

The tradeoff is dry heat. In Arizona, I noticed rubber fuel lines and gaskets dried out and cracked faster than they did in Ohio, even though the fuel itself stayed in better shape.

A cracked fuel line is its own separate problem. It can leak small amounts of fuel and let extra air into the system, which affects how the engine runs even with perfectly good gas. If you live somewhere hot and dry, like Phoenix or Las Vegas, check your fuel lines every year or two regardless of what you do with the fuel itself.

Mowers in these climates also tend to sit idle for less time overall. Some homeowners in the Southwest mow year-round at a slower pace, so the whole question of winter storage matters less. If your mower never truly sits idle for more than a few weeks, stabilizer alone is usually enough.

Humid Storage Sheds and Rust Risk

Humid storage sheds raise rust risk on metal parts like the mower deck, blade, and any exposed bolts, separate from whatever is happening with the fuel. A Georgia shed with no climate control holds moisture in the air all winter long.

I found surface rust starting on a mower deck after just one humid Georgia winter, something that never happened during six years of Ohio winters. Wiping the deck with a light coat of oil before storage helps a lot here.

A quick spray of light machine oil or even a rag with a little WD-40 on the underside of the deck goes a long way. Grass clippings trap moisture against metal, so cleaning the deck thoroughly before storage matters just as much as the oil coating afterward.

I also learned to store the mower with the deck slightly elevated on two wood blocks in my Georgia shed. It keeps air circulating underneath instead of trapping ground moisture directly against the metal all winter. It is a small trick, but it made a visible difference the following spring.

Compression Table: Climate Zone Risks

Common Questions People Get Wrong

People get a few things wrong again and again when it comes to winter mower storage. These are the two I hear most often from neighbors and readers.

Is It Bad to Store a Mower With Gas In It

Yes, it is bad to store a mower with plain gas in it for months without stabilizer, especially ethanol gas. The fuel starts breaking down within 30 to 60 days and can cause carburetor gumming or ethanol separation by spring.

It is not automatically ruined after one winter, though. If you add stabilizer before storage, gas can safely sit for up to a year in most cases, according to Sta-bil’s own product guidance (Sta-bil, 2024).

I get this question a lot from people who just moved into a new house and inherited a mower with unknown gas already in the tank. My advice is simple: if you do not know how old the gas is, drain it and start fresh. It is not worth guessing with something that costs so little to just replace.

Does Stabilizer Really Work as Well as Draining

Stabilizer works nearly as well as draining for most home mowers stored three to five months. It will not perform miracles on gas that already sat untreated for weeks before you added it, though.

Stabilizer needs to go into fresh or recently added gas to work correctly. Pouring it into gas that already smells sour or has separated will not undo the damage that already happened.

Think of stabilizer like sunscreen. It prevents sunburn if you apply it before you go outside. It does nothing for the sunburn you already have. That is roughly how stabilizer behaves with fuel that has already started breaking down.

Pros and Cons: Running Dry vs. Stabilizer

My Final Recommendation

After testing both methods across three different climates, I run my mower dry every single fall now. It costs nothing, it takes 15 minutes on a Saturday afternoon, and I have not had a hard spring start since I started doing it consistently.

That said, I keep a bottle of Sta-bil in my garage for the years I run out of daylight or forget until the weather turns. Stabilizer is not a downgrade. It is a smart backup plan, and for a lot of homeowners with busy fall schedules, it might honestly be the better everyday choice.

Whatever you pick, do not skip it entirely. The mower that sat with a full tank of ethanol gas in my shed one October taught me that lesson the hard way, and I would rather you learn it from this article than from a mower that won’t start next April.

Frequently Asked Questions About Running a Mower Out of Gas

Should I run my lawn mower out of gas before winter?

Yes. Running the tank dry before winter prevents old fuel from gumming up the carburetor and stops ethanol separation from happening at all, since there is no fuel left to separate.

How long can gas sit in a mower before it goes bad?

Untreated gas typically starts breaking down within 30 to 60 days. Adding a fuel stabilizer before storage can extend that safely to around 12 months in most cases.

Is fuel stabilizer better than draining the tank?

Neither is universally better. Draining protects the carburetor completely and costs nothing, while stabilizer is faster and keeps the mower ready to run again without a fill-up.

Can I just add stabilizer to old gas that already sat all summer?

No. Stabilizer needs to be added to fresh or recently purchased gas. It slows future breakdown but cannot reverse damage that already happened to old fuel.

What is ethanol separation and why does it matter?

Ethanol separation happens when the ethanol in gas absorbs moisture from the air and separates from the gasoline. It leaves a watery layer at the bottom of the tank that will not burn properly in your engine.

Do I need to change the oil before winter storage too?

Yes. Old oil holds moisture and small metal particles that cause extra friction the next time you start the engine. Change the oil every fall regardless of what you do with the fuel.

Will my mower be damaged if I forget to prep it before winter?

Not permanently, in most cases. A gummed-up carburetor can usually be cleaned out by a small engine shop for $50 to $100, but it is a hassle you can avoid with 15 minutes of prep in the fall.