Lawn Mower Winter Storage

As the mowing season winds down, taking the time for proper lawn mower winter storage is one of the most important maintenance tasks you can perform. Storing your mower correctly protects your investment, prevents frustrating starting problems in the spring, and extends the life of the engine. The process, often called winterizing, involves a series of steps to safeguard the fuel system, battery, and mechanical components from the damaging effects of cold, moisture, and inactivity. This guide walks you through the essential tasks, based on guidance from major engine manufacturers and safety standards.

Fuel System: To Stabilize or Run Dry?

The most critical step in lawn mower winter storage is addressing the fuel. Modern gasoline, especially blends containing ethanol, can degrade and leave behind gummy deposits and varnish that clog the carburetor and fuel lines. You have two primary options, and the correct choice depends on your mower’s design and your operator’s manual.

For most modern mowers with a carburetor, the recommended method is to add a fuel stabilizer. First, fill the tank with fresh gasoline to minimize air space, which reduces condensation. Then, add the correct amount of fuel stabilizer for the tank’s capacity, following the product’s instructions. Run the engine for several minutes to circulate the treated fuel throughout the entire fuel system. This keeps the gasoline chemically stable for months.

Some manuals may instruct you to run the engine until the fuel tank is completely empty. This method prevents old fuel from sitting in the system. However, it’s crucial to follow your manual, as some fuel-injected or specific engine models should not be run dry. Never leave a tank partially full of untreated fuel over winter. For more on fuel-related starting issues, see our guide on common causes of a mower that won’t start.

Oil, Spark Plug, and Blade Maintenance

After the final mow, perform these key engine and cutting maintenance tasks before storage.

Change the Oil

It’s best to change the oil before storage, not after. Used engine oil contains contaminants and acids that can corrode internal engine components over a long period of inactivity. Changing it ensures fresh, clean oil protects the engine all winter. Run the engine for a few minutes to warm the oil first, making it easier to drain completely. For a detailed schedule, read our article on how often you should change lawn mower oil.

Consider the Spark Plug

This is an excellent time to remove and inspect the spark plug. Check its condition and electrode gap, cleaning it or replacing it if it’s worn. Before reinstalling the plug or installing a new one, add a small amount of engine oil into the spark plug hole and gently pull the starter cord a few times (with the plug wire disconnected) to coat the cylinder walls for added protection against rust. Always reconnect the spark plug wire securely.

Sharpen and Balance the Blade

A dull blade tears grass, leaving it vulnerable to disease over the winter and resulting in a ragged lawn in spring. Remove the blade, sharpen it properly, and ensure it’s balanced before reinstalling it tightly. A sharp blade is safer and more efficient. Our guide on how to sharpen lawn mower blades walks you through the process. Also, take this opportunity to clean the mower deck thoroughly to prevent rust and corrosion.

Battery Storage for Winter

If your mower has a battery, neglecting it over winter is a leading cause of failure. For lead-acid batteries, the best practice is to remove the battery and store it indoors in a cool, dry place, away from potential freezing temperatures. Charge it fully first, and then place it on a non-conductive surface like a wooden shelf. Connect it to a maintenance charger or battery tender designed for small engines, which provides a trickle charge to keep it at optimal voltage. Check the charge level monthly and recharge if needed. Always follow the battery manufacturer’s specific storage instructions. Proper care is part of a complete lawn mower maintenance routine.

Final Cleaning and Covering

A thorough cleaning prevents dirt and grass clippings from holding moisture against the metal, which leads to rust and corrosion. Use a brush or putty knife to scrape off caked-on debris from the deck, undercarriage, and engine cowling. Wipe down all surfaces with a damp cloth. Let the mower dry completely before covering or storing it.

While a breathable, fitted mower cover is ideal to keep dust off, avoid using a plastic tarp or non-breathable cover in a damp environment, as it can trap moisture and promote mold and rust. If your storage area is dry and dust-free, covering may not be necessary.

Choosing a Safe Storage Location

Where you store your mower is as important as how you prepare it. The ideal location is a clean, dry, and well-ventilated area like a shed or garage.

Following these storage criteria helps ensure your mower is safe and ready for its spring preparation.

Frequently Asked Questions

Should I drain gas from my lawn mower before winter?

The guidance varies. For most mowers, adding a fuel stabilizer to a full tank is the preferred method, as recommended by many engine manufacturers. This prevents corrosion and keeps fuel from degrading. Some manuals may instruct you to run the carburetor dry. You should never leave a tank partially full of untreated gasoline over winter, as it will almost certainly cause starting issues. Always check your specific operator’s manual for the correct procedure.

Can I just leave the battery in the mower over winter?

It’s not recommended. A battery left connected in a cold mower will slowly discharge and can freeze, causing permanent damage. For the longest battery life, remove it, charge it fully, and store it indoors on a maintenance charger. This simple step is a key part of preventative troubleshooting.

Is it necessary to change the oil before storing the mower?

Yes, it is highly recommended. Changing the oil after the last use removes acidic contaminants and moisture from the engine. Fresh oil provides a protective coating on engine internals during months of inactivity, preventing corrosion. It’s one less task to worry about when you’re eager to mow in the spring.

What if I forgot to winterize my mower last fall?

If you discover an unprepared mower in spring, start by checking the fuel. If old gas is present, you’ll likely need to drain the tank and carburetor and refill with fresh, stabilized fuel. Check the oil level and condition, inspect the spark plug, and ensure the battery is charged. Be prepared for the possibility of a clogged carburetor jet, which may require cleaning. Our maintenance tools guide can help you assemble what you need for the job.

How long can a mower sit without being used?

A properly winterized mower can sit for several months over winter without issue. The problems arise from improper storage. Untreated fuel can begin to degrade in as little as 30 days, leading to deposits. A battery left disconnected but not maintained can sulfate and lose capacity within a few months. Following the storage steps outlined here allows your mower to sit idle for the off-season safely.