Winterizing Your Lawn Mower

By Allyn Hane - "The Lawn Care Nut"
November 6, 2021

Seems like this lawn season has gone by so fast this year doesn’t it? It seems like it was just last week that I was filming an epic throw-down showing you the easy way to apply Milorganite to your lawn. I made that video in later May, over 5 months ago!

And while there are still quite a few parts of the country where you can still apply some late-season Milorganite, a good majority of you are already at the end of your season and are wondering just what to do to winterize and prepare your mower in prep for winter.

I’m going to give you the checklist that I used to run through when I lived in Indiana.

cleaning grass off of mower

Cleaning under the deck is often overlooked but very important. Buildup like you see here can have a negative impact on your mower’s mulching or bagging performance.

Basic Winterization Checklist for Your Lawn Mower

  • Clean under mower deck, sharpen mower blade
  • Change Engine Oil
  • Inspect and change filters if needed (see your operators manual)
  • Inspect and/or replace spark plug (see your operators manual)
  • Stabilize fuel and fuel system

The part I want to focus on is the last bullet point there about stabilizing your mower’s fuel and fuel system. If you have had “hard starts” in the spring or had mowers just completely stop working after winter, following these tips should help.

Adding a stabilizer is important because fuel can go bad if it is left sitting too long. In fact, in as little as 30 days the fuel sitting in your mower or gas can begin to deteriorate. Over time this can leave behind gums, varnish, and other solids that interfere with flow in your system. Fuel stabilizers stop this buildup and also help reduce water separation in fuels that contain ethanol.

screw on a lawnmower

When winterizing your mower, it’s a good idea to look for grease points. These are usually found around the wheels. Not all mowers have them but if you do this is a good time to grease them up!

Two Ways To Utilize Fuel Stabilizers

When I first started learning DIY lawn care and taking care of my equipment, I was living in NW Indiana. In “normal” weather years I’d perform my last mow of the season sometime in mid-to-late November and I would not start back up again the following season around early March. That’s about 4 months off. Here is how I’d prepare my mower’s fuel system heading into winter.

  • Early November I would get 1-2 gallons of fresh fuel from the pump and fill my small gas can.
  • Add fuel stabilizer to that fresh gas in the can.
  • Fill up my mower with this fresh gas in early November and mow as normal all month.
  • Once I performed my final mow of the season at the end of November, I’d completely run the mower dry. Just run it until all the gas is gone.
  • Store mower for winter.

The reason I use the fuel stabilizer in this scenario is that I want all that chemistry to coat the internal parts of the fuel system and if any gas does remain after I ran it dry, it will be all good. You’ll probably have some gas left in your can too. Since there is a stabilizer in it you know it will be all good to use for your snowblower, or even into next spring. And if you don’t want to store it anyway, just put it in your car.

However, there is one drawback to this strategy and that is that your mower is pretty much out of commission at this point, unusable.

The thing about that is what happens if you get a big push of leaves onto your lawn in mid-December? You’re not going to have your mower available for some easy bagging.lawn mower fuel stabilizer

Fuel stabilizers keep gas from going bad and gumming up your fuel system. They also prevent water build up from phase separation.

Another thing that often happens is you get a late warm spell in December and the grass starts growing again. You will have the urge and the need to mow, but you can’t. This can be emotionally tough to deal with.

So what I started doing later on, and what I recommend for many of you, is to winterize this way:

  • Early November. 1-2 gallons of fresh fuel from the pump in a gas can.
  • Add fuel stabilizer to that fresh gas in the can.
  • Fill up mower with this fresh gas in early November and mow as normal.
  • After every mow, fill mower completely to the top with fresh, stabilized fuel.
  • Every 30 days during winter, take mower outside, crank it and let it run for 5-7 minutes.
  • Top off the tank after each of these cycles.

The key to this is that you now have access to the mower anytime you need it. So if that late December leaf cleanup is required, the mower is ready to go. You have fuel that is protected by the stabilizer and you are keeping the tank full which discourages water buildup (phase separation). And on top of that, you are running the machine every 30 days which will burn and replace the fuel that has been sitting in the carb bowl and lines.

Plus, if you think about it, if your mower has been starting fine every 30 days all winter, it’s logical that it’s going to give you an easy start in March too.

One Solution To All

One final solution to all of this is to go electric. Just think about it, if you have a battery mower all of the above hassles is eliminated. More and more I see the technology in batteries improving and if you are someone who doesn’t like this kind of maintenance, then it’s for sure something to consider.

Either way, I hope you have a short and mild winter wherever you live and that spring is upon you before you know it! I’ll see you in the lawn!