Lawn Mower Winterizing: Step-by-Step Storage Checklist

Lawn mower winterizing is a set of end-of-season tasks that protect your engine, fuel system, and cutting components during months of storage. A complete winterizing checklist covers: treating or draining fuel, changing the oil, inspecting or replacing the spark plug, cleaning and protecting the deck and blade, checking belts and cables, and storing or maintaining the battery. Done in order, these steps take under an hour and prevent the most common cause of spring starting failures.

Key Takeaways:

• Stale, ethanol-blended fuel is the single biggest cause of hard spring starts. Address the fuel system first.
• Change the oil before storage, not in spring. Used oil carries acidic combustion byproducts that corrode engine internals during long sit periods.
• A fresh or inspected spark plug saves a diagnostic headache in March.
• Lead-acid riding mower batteries should be removed and kept indoors or connected to a battery tender. Lithium-ion battery mower packs store best at around 40 percent charge in a temperature-stable space.
• Never skip the deck cleaning step. Trapped grass moisture accelerates rust on the undercarriage faster than almost anything else.

The last mow of the season is easy to forget. Once the grass stops growing, most homeowners push the mower into the shed and move on. The problem is that a mower left unprepared through winter accumulates damage that shows up in April as a no-start, a rough idle, a corroded battery, or a blade that tears instead of cuts. Lawn mower winterizing exists to prevent every one of those outcomes.

This checklist works for gas-powered push mowers, self-propelled walk-behinds, and gas riding mowers. Where battery-powered or cordless mowers require a different approach, we note that clearly. Follow these steps in order, once the season is truly done and night temperatures are consistently below 50 degrees F in your area.

Step 1: Address the Fuel System First

Fuel is where most winterizing mistakes happen, and fixing a gummed carburetor in spring costs far more time and money than treating the fuel in fall. The core issue is ethanol. Most pump gasoline sold in the United States is E10, meaning it contains up to 10 percent ethanol. Ethanol attracts moisture, and over a storage period of 30 to 90 days, it can separate from the gasoline, corrode fuel lines, and leave gummy varnish deposits in the carburetor’s small jets and passages.

Per the U.S. Department of Energy’s Alternative Fuels Data Center, E15 (gasoline blended with up to 15 percent ethanol) is prohibited for use in lawn mowers and other small off-road engines. The pump label often reads “Unleaded 88” and looks like a routine choice. It is not appropriate for your mower’s fuel system. Check the pump before filling any gas can.

You have two valid approaches to fuel winterizing, and your mower’s owner manual will specify a preference:

Option A: Add Fuel Stabilizer and Run It Through

This is the approach Briggs and Stratton recommends for most of their engines. Fill the tank with fresh fuel (top it off, since a partially full tank allows more air and moisture contact) and add a fuel stabilizer at the ratio specified on the product label. Run the engine for 10 minutes so that the stabilizer-treated fuel circulates through the entire fuel system, including the carburetor bowl. This prevents both the gumming that ethanol causes and the varnish that results from fuel evaporating out of an empty system.

As Honda Power Equipment states in their fuel recommendations, the fuel tank should not hold untreated gasoline for more than 90 days of inactivity. After adding the stabilizer, Honda recommends running the engine outdoors for at least 10 minutes to ensure treated fuel has displaced untreated fuel throughout the entire system.

Option B: Drain the Fuel System Completely

Some manufacturer manuals, particularly for carbureted engines on older or simpler equipment, specify draining all fuel from the tank and then running the engine until it stalls on its own from fuel starvation. This eliminates the risk of varnish buildup, though it requires restarting with fresh fuel in spring and may leave a very thin residual film in the carburetor if not executed carefully. If you go this route, confirm in your specific manual that it is the preferred method, since running a carbureted engine completely dry is not recommended by all manufacturers.

✅ Quick action: Fuel system

• Check the pump label. Never use E15 (Unleaded 88) in a small engine.
• Choose stabilizer treatment or full drain based on your owner manual’s recommendation.
• If using stabilizer: top off the tank, add stabilizer, and run the engine for 10 minutes.
• Also replace the fuel filter at this step. It is already in-line and takes only a few minutes. See our guide to lawn mower fuel filter replacement for the correct procedure.

Step 2: Change the Oil Before Storage, Not in Spring

There is a common debate about whether to change oil in fall or wait until spring. The case for fall is straightforward: used engine oil accumulates combustion byproducts over a mowing season, including acids that form when fuel burns. Leaving that oil in contact with internal engine surfaces for four to six months of storage allows those acids to quietly corrode the cylinder walls, bearings, and other components. Starting the spring with that old oil already in the engine means the damage has been happening since November.

Drain the oil while the engine is still warm from the fuel stabilizer run (warm oil flows out more completely than cold oil). Position an oil drain pan under the drain plug, remove the plug, and allow the oil to drain fully. If your mower has an oil filter, replace it at this step. Refill with fresh engine oil to the level specified in your manual, using the viscosity grade appropriate for your climate. For most residential use, Briggs and Stratton recommends SAE 30 for warm climates and SAE 10W-30 or synthetic 5W-30 for variable temperatures. Always confirm the correct grade in your specific engine manual before filling.

After refilling, start the engine briefly (about one minute) to circulate the fresh oil before storing the mower. This coats the internal surfaces with clean oil for the winter.

✅ Quick action: Oil change

• Drain oil while the engine is warm, immediately after the fuel stabilizer run.
• Replace the oil filter if your mower has one.
• Refill with the manufacturer-specified oil type and quantity. Do not overfill.
• Run the engine for about one minute to circulate the fresh oil before shutting down.

Step 3: Inspect or Replace the Spark Plug

The spark plug is one of the cheapest parts on the mower and one of the most common reasons for a difficult spring start. Inspecting or replacing it at winterizing time means one less variable to troubleshoot in spring, when you just want the machine to run.

Disconnect the spark plug wire first. This is not optional: it prevents accidental engine startup while your hands are near the blade or engine components. Remove the plug with a spark plug socket and examine the electrode tip. A light tan or gray color on the electrode indicates normal combustion. Black, sooty deposits suggest the engine has been running rich (too much fuel, not enough air). Oil fouling (wet, oily deposits) may indicate engine wear that warrants a closer look by a technician before spring.

If the plug is damaged, fouled, or shows significant electrode wear (a rounded or eroded electrode tip), replace it rather than reinstalling it. For the correct replacement plug type and gap specification, refer to your engine model’s documentation. Our detailed guide to lawn mower spark plug replacement and gap settings covers how to read plug condition and set the correct gap for common small engine models.

After inspecting or replacing the plug, some technicians recommend spraying a short burst of fogging oil (a storage-specific protective spray available at auto parts and outdoor power equipment retailers) into the cylinder through the spark plug hole. This coats the cylinder wall with a thin oil film that prevents rust during storage. If you use fogging oil, do not reinstall the plug wire until you are ready to use the mower in spring.

✅ Quick action: Spark plug

• Disconnect the spark plug wire before doing anything else under the deck or near the engine.
• Remove, inspect, and replace the plug if the electrode is fouled, damaged, or visibly worn.
• Optional: spray fogging oil into the empty cylinder for rust protection during storage.
• Leave the plug wire disconnected through storage for safety.

Step 4: Clean and Protect the Deck and Blade

Trapped grass clippings and moisture are the fastest path to deck rust and blade deterioration. With the spark plug wire still disconnected, tilt the mower (or use a lift on a riding mower) to access the undercarriage. Scrape away any packed grass from the deck using a plastic scraper or wooden stick. Do not use your hands near the blade. For stubborn debris, a garden hose or compressed air works well once the mechanical scraping is done.

After cleaning, spray the underside of the deck with a light coat of a water-displacing spray or dedicated mower deck protectant (check the product label to confirm it is safe for metal decks). This creates a barrier against moisture during storage. Do not apply oil-based products to plastic deck components.

Inspect the blade edge for nicks and dullness. If the blade needs sharpening, winter is the ideal time to address it, so the mower is ready to cut cleanly on the first use in spring. Our guide to push mower blade sharpening covers the correct technique for walk-behind mowers. For riding mowers, the deck must be fully disengaged and the blade removed safely before sharpening.

✅ Quick action: Deck and blade

• Always disconnect the spark plug wire before working under the deck.
• Scrape and rinse all accumulated grass clippings from the undercarriage.
• Apply a light protective coating to the deck’s underside to prevent rust.
• Sharpen or note the condition of the blade for spring. A dull blade tears grass rather than cutting it cleanly.

Step 5: Inspect Belts, Drive Cables, and Moving Components

The end of the season is the right time to catch belt wear before it becomes a spring failure. Belts that are cracked, glazed (shiny on the inner surface), frayed at the edges, or visibly stretched should be replaced before storing the mower. Replacing a belt with the mower already out for winterizing is much easier than diagnosing a no-drive or no-engage condition on a spring morning.

On self-propelled walk-behind mowers, check the drive cable for kinks, fraying, or a loose connection at the handle bail. A drive cable that is out of adjustment or partially frayed may work in summer when it is warm and pliable but fail when spring temperatures are still cool, and the cable is stiff.

On riding mowers and zero-turn mowers, inspect the deck drive belt (the belt that powers the cutting blades) and the ground drive belt (the belt that moves the mower forward). Check for cracks or glazing. Ariens’ maintenance documentation recommends inspecting mower belts and replacing them as needed at seasonal storage, noting that worn belts are better identified before storage than during the first mow of the season.

Lubricate any grease fittings (also called zerks) on the mower deck spindles, wheel bearings, and steering components as specified in your owner manual. Most manufacturers specify a lithium-based grease for these points. Using the wrong lubricant or skipping this step can cause spindle bearing wear during the first heavy use of spring.

✅ Quick action: Belts and cables

• Inspect all belts for cracks, glazing, and fraying. Replace any belt that shows these signs.
• Check self-propelled drive cable for kinks or fraying at the handle end.
• Grease all fittings on the deck, spindles, and steering components per your manual’s specifications.

Step 6: Battery Storage (Gas Riding Mowers and Battery-Powered Mowers)

Battery care is the step most homeowners skip, and it is one of the most common reasons a riding mower or cordless electric mower fails to start the following spring. The approach differs significantly depending on battery type, so knowing what you have matters.

For lead-acid batteries (the 12-volt battery on most gas riding mowers), Ariens recommends removing the battery and storing it in a dry, cool location, noting that batteries can freeze if they discharge during cold storage. If the mower stays in an unheated garage, connecting a battery tender (a maintenance charger that supplies a small float charge without overcharging) is the more practical approach than removing the battery entirely. A standard trickle charger without maintenance circuitry can overcharge a battery if left connected for months. Use a charger specifically rated as a “smart” or “maintenance” charger for long-term storage.

For lithium-ion battery packs on cordless electric mowers, Consumer Reports advises storing lithium-ion batteries at approximately 40 percent charge, in a location that stays between 40 and 80 degrees F. Charging a lithium-ion pack to 100 percent and leaving it there for months creates cell stress that shortens the battery’s usable life. Always check your specific battery manufacturer’s documentation for their exact storage guidance, since some brands build auto-discharge circuitry into their packs while others require manual charge management.

✅ Quick action: Battery

• Lead-acid (riding mower): remove and store indoors, or connect a smart battery tender.
• Lithium-ion (battery mower): charge or discharge to approximately 40 percent, remove from mower, store indoors between 40 and 80 degrees F.
• Never store any battery type directly on a concrete floor. Use a wooden shelf or a bench to buffer temperature fluctuations.
• Check for signs of corrosion on lead-acid terminals before reconnecting in spring. Clean and coat terminals as needed.

Step 7: Final Cleaning and Storage Setup

Before moving the mower to its storage position, clean the engine shroud and cooling fins. Small engines are air-cooled, meaning the fins around the cylinder head must be clear of debris to dissipate heat. A season of mowing leaves grass, dirt, and debris packed into those fins. Remove it with a brush or compressed air (with the spark plug wire disconnected). Caked debris on the cooling fins can contribute to overheating in the first heavy-use sessions of spring.

Wipe down the engine exterior with a clean rag. Apply a light spray of a water-displacing product to any exposed metal components susceptible to surface rust, particularly on the engine block exterior and any exposed steel frame members.

Store the mower in a dry, covered space. A dedicated lawn mower cover adds protection against dust and incidental moisture even inside a garage or shed. If storing in a space that is not climate-controlled, avoid positioning the mower against an exterior wall where temperature fluctuations are greatest.

Do not store a gas mower near a furnace, water heater, or other open-flame heat source. Even stabilized fuel produces vapors, and those vapors are flammable.

Complete Lawn Mower Winterizing Checklist

Use this checklist as your single reference before closing up the storage space for the season. Print it or keep it on your phone. Each item should be checked off in order, because several steps build on the previous one (you need a warm engine for the oil drain, you need the plug wire off before the blade work, and so on).

Safety Points: When to Stop and Call a Technician

Most of what is covered in this checklist is appropriate for a homeowner to do without specialized tools. These situations are exceptions.

• If you see oil fouling on the spark plug (wet, oily deposits on the electrode and insulator), this can indicate a worn piston ring or valve seal. Do not simply replace the plug and assume the problem is solved. Have a certified small-engine technician inspect the engine before the next season’s use.
• If the mower blade is bent or cracked, do not attempt to straighten and reinstall it. A bent blade is out of balance, and an out-of-balance blade at cutting RPM creates dangerous vibration. Replace it, or have a technician do so.
• If the fuel system shows signs of significant corrosion (rust flakes in the fuel tank, visible deterioration of fuel lines), do not treat and store the mower without addressing this. A corroded fuel system requires professional service to clean or replace components safely.
• If the lead-acid battery shows signs of swelling, leaking, or significant internal corrosion, do not attempt to charge or reinstall it. Dispose of it safely at a battery recycling facility and replace it with the correct replacement before spring use.
• If you are unsure about any step in this process, consult your owner’s manual or contact your equipment dealer. Winterizing done incorrectly (such as using the wrong oil viscosity, incompatible fuel additives, or an improperly specified replacement part) can cause more damage than skipping a step.

When Winterizing Fits Into the Broader Seasonal Lawn Care Cycle

Lawn mower winterizing is one part of a larger seasonal lawn care calendar. Winterizing protects the equipment side of that cycle. The companion piece in spring is a pre-season tune-up, and our pre-season mower tune-up guide covers everything you will want to check when bringing the mower back out of storage. If you have a battery-powered mower and want a deeper look at cold-weather considerations, including how to approach the final mow before winter, our guide to cold weather mowing covers the decisions most homeowners face in late fall.

For gas mower owners who want to understand the fuel stabilizer options in more detail before buying, our mower fuel stabilizer guide compares how different products work and which situations each is suited for.

FAQ’s

This article is for general informational and educational purposes only. It has been compiled from manufacturer guidelines, industry standards, and published horticultural research. Always follow the safety instructions in your specific equipment’s owner manual. For chemical applications, follow product label directions and consult your local cooperative extension service for region-specific guidance.