Preparing Your Lawn Mower for Winter

by Murray Anderson
DIY Landscaping for Less photo

Perform these maintenance tasks at the end of fall and you can minimize the aggravation and cost of trying to get your lawn mower working again next spring.

I hate cutting my lawn! I would hate it even more if I had to fight to start my lawnmower.

Since I don’t like struggling with machines, and even more don’t like the idea of paying someone to do something I can do, I have developed a small set of procedures to prepare your lawnmower for winter. If you do these simple things, you won’t have to waste your time trying to start your machine, or, even worse, hauling your mower to the repair shop and paying somebody to fix it.

Small engines that are just put away in the fall can be very cranky and hard to start six months later. Gasoline that is left in a mower can gum up the carburetor and fuel system and make a mower refuse to start. A balky engine is the last thing you want to deal with, especially when all you really want is to cut your lawn and get on with your life.

So, here’s how to minimize your aggravation next spring.

Replace the Oil

This fall, after you have given your lawn its final cut, take an hour to prepare your mower for next year.

If your mower has a 4-cycle engine (the fuel you use is gasoline only), the first thing to do is to drain the motor oil. Do this while the engine is still warm. This ensures that any impurities that are in suspension in the oil are drained right out of the engine.

Then refill the crankcase with fresh oil (probably 10W30 or the grade your owner’s manual calls for).

If you have a 2-cycle engine (your lawnmower uses a mixture of gas and oil), your motor doesn’t have a crankcase. The oil in the fuel mixture lubricates the engine, so you obviously won’t need to do this.

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Drain or Stabilize the Gas

Once the engine is cool, drain the gas tank.

After draining the tank, start the engine and let it run on the gasoline remaining in the carburetor until the mower stops because it’s out of gas. Running the engine out of gas will make sure that you don’t get any build-up of “gunk” in the carburetor or fuel system, and also forces you to use fresh gas in the spring.

An alternative method is to fill up the tank now, and then add an after-market product (stabilizer) to the gas. This additive is designed to stop the build-up of gum in the carburetor and fuel system. It’s available at hardware stores or automotive stores. However, I have always found that running the mower out of fuel works well, and the bonus is that I don’t have to worry about a gas tank full of fuel being stored in my shed.

Clean/Replace the Air Filter and Spark Plug

Now is the time to clean or replace the air filter on the mower as well. Follow the instructions in your owner’s manual.

The next step is to remove the spark plug. A spark plug wrench is your best tool, but you can use a pair of vice grips or a crescent wrench on the metal base of the plug. Turn gently. Remember that spark plugs can break. After removing the plug, put a few squirts of motor oil into the spark plug hole, and without replacing the spark plug, slowly pull on the starter cord to turn the engine over a few times. This distributes the oil you just squirted in on cylinder walls and valves, preventing rust inside the engine.

While it is in your hand, clean the spark plug, or if it’s a couple of years old, get a new one. If you replace it, make sure you get an exact match. Spark plugs are not all the same, and the wrong plug can actually damage your machine. Take your old plug to the store with you to ensure you get an exact match. Put the spark plug (hand tight) back into the mower. Now, you won’t forget where it is next spring.

Clean the Mower

To keep your mower looking good, and make sure it doesn’t rust, don’t put it away dirty.

Scrape off any build-up of grass clippings on the underside, and clean the engine surface and mower deck.

Finally, put your newly cleaned mower away somewhere that it is protected from the elements and animals.

Come next spring, all you will need to do is tighten the spark plug, fill the tank with fresh gas and start your engine. The oil you squirted into the spark plug hole will make the exhaust smoky for a few minutes until is burned up, but it won’t cause any harm.

The best part of going through this process now is you won’t have to waste any time next spring struggling with a mower that won’t start. Following this simple process has kept my 20-year-old Craftsman mower running. It has never needed professional servicing and just keeps on going.

You, too, will be able to start your mower up, cut your lawn and get on with enjoying that new spring weather. No fights with a balky engine and no trips to the service shop.

Reviewed October 2023

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