I have spent over two decades in the shop listening to the sound of heartbreak. Every single spring, my phone starts ringing off the hook with the same story: 'Derick, my mower won't start after sitting all winter.' It is almost always a preventable issue caused by letting the machine sit improperly. Winterizing isn't just about covering your mower with a tarp; it is about preserving the life of your equipment so it is ready to roll when the first blade of grass pops up in March. In this guide, I will walk you through exactly how I winterize the mowers that come into my shop so you can do the same at home.
Why Winterization Matters
Think of a lawn mower engine as a living machine. When you leave old gasoline in the tank, it begins to break down. Modern fuel contains ethanol, which attracts moisture from the air. Over a long, cold winter, that moisture separates from the fuel, turns into a gummy varnish, and clogs your delicate carburetor jets. By the time spring arrives, that fuel is essentially sludge. Beyond fuel, moisture is the enemy of your battery and deck. Taking a few hours in the fall to clean and prepare your machine is the best insurance policy you can buy for your lawn equipment.
Step 1: The Fuel System
Safety First: Always disconnect the spark plug wire before performing any maintenance to prevent accidental starting.
You have two choices here, and both are acceptable if done correctly. Option one is to drain the fuel system entirely. Use a siphon pump to get the bulk of the fuel out of the tank, then run the engine until it sputters and dies to clear the lines and the carburetor bowl. Option two is to fill the tank to the top and add a high-quality fuel stabilizer. Filling the tank prevents condensation from forming on the internal tank walls. If you use a stabilizer, run the mower for 5-10 minutes to ensure the treated fuel has reached the carburetor.
Step 2: The Oil Change
Never leave dirty oil sitting in your engine over the winter. Combustion byproducts—like carbon and microscopic metal shavings—mix with the oil and create acidic compounds. Over several months, these acids can actually etch the internal engine components, like your cylinder walls and bearings. Change your oil and oil filter before you park it for the season. Fresh, clean oil provides a protective layer that keeps internal parts corrosion-free during the long storage period.
Step 3: Cleaning the Undercarriage
After years of working on these machines, the worst thing I see is a rotted-out mower deck. Grass clippings are essentially wet sponges. If you leave a layer of caked-on grass under your deck, it holds moisture against the metal all winter long. This leads to rust, which ruins your deck’s integrity and ruins your discharge patterns. Take the time to scrape the deck clean. I use a plastic scraper to avoid damaging the finish, though a pressure washer on a low setting can work if you are very careful not to spray directly into the spindle bearings.
Pro Tip: Apply a light coating of silicone spray or a thin film of oil to the underside of your clean, dry mower deck to prevent grass from sticking next season.
Step 4: Battery Maintenance
Lead-acid batteries lose charge over time, even when not in use. If a battery is left in a state of partial charge in freezing temperatures, the internal chemistry can fail, or worse, the electrolyte can freeze and crack the casing. Remove the battery and store it in a cool, dry place—preferably on a trickle charger or a battery maintainer. If you prefer to leave it in the mower, disconnect the negative terminal cable to prevent a slow drain from parasitic loads like digital hour meters.
Step 5: Lubrication and General Inspection
Before you put the cover on, check all your grease points. Most modern riding mowers have zerk fittings on the front axle and spindle assemblies. Pushing new grease into these points forces out any water that might have entered through the seals during the mowing season. While you are at it, check your tire pressure. If a tire is low, the rim can sit on the ground, potentially causing a flat spot or premature rot on the tire sidewall.
Common Mistakes to Avoid
One common mistake I see is leaving the mower out in the elements. If you do not have a garage or shed, use a breathable cover rather than a plastic tarp. A plastic tarp traps moisture underneath, creating a literal greenhouse for rust. Another mistake is forgetting the air filter. A dirty air filter is a magnet for moisture; replace it now so you are ready to go in the spring.
When to Call a Pro
If you find a major oil leak, hear unusual grinding noises from the transmission, or if the mower has been sitting for multiple years, it might be time to bring it to a shop. Sometimes, deep-seated issues require specialized tools like a compression tester or a leak-down gauge. There is no shame in letting a professional handle the heavy lifting if you are not comfortable tackling these tasks yourself. Remember, preventative maintenance is always cheaper than a major mechanical overhaul.