How to Use Fuel Stabilizer When Storing Your Mower for Winter

Shop Part No. TY27534

Properly caring for your mower before storing it for the winter is key to ensuring it remains in good shape when the next mowing season rolls around. Using a fuel stabilizer is one of the most effective ways to protect your engine and fuel system from damage during long periods of inactivity. In this guide, we'll walk through how to properly use a fuel stabilizer and, for those without one, install a fuel shutoff valve to complete the winterization process.

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About Fuel Stabilizer

Fuel stabilizer isn’t just for winter—it’s a good practice to use it year-round. It helps keep your fuel fresh and your fuel system lubricated and conditioned. Most stabilizers contain cleaners that reduce the negative effects of ethanol in gasoline, which can be harmful to your mower over time. Whenever possible, we recommend using non-ethanol fuel in your mower, but if that’s not an option, a stabilizer is a great backup.

Pictured below, you'll see we are using John Deere’s Fuel Protect (part no. TY27534), which is specifically designed for gasoline engines. It helps prevent ethanol-related problems and keeps the fuel in good condition during storage. Multiple brands of fuel stabilizers are available, but the process of using them is generally the same—just be sure to follow the instructions for mixing the right amount of stabilizer for your mower’s fuel tank capacity.

For example, on this John Deere X320, which has a 3.5-gallon fuel tank, the instructions recommend mixing one ounce of stabilizer for every two gallons of fuel. So, you will need about 1.75 ounces.

Adding Stabilizer into Fuel

It's best to add a stabilizer to your fuel tank when it's not entirely full, as this will allow you to add fresh gasoline to help it mix properly.

Say your mower has about half a tank of fuel. In this case, you would start by pouring in an appropriate amount of stabilizer (around 2 ounces). Most fuel stabilizer bottles, like this one, feature a sight gauge on the side that shows you how much you’re pouring without needing a separate measuring cup.

After adding the stabilizer, top off the tank with fresh gasoline. It’s best to fill the tank as much as possible—up to about the midpoint of the filler neck. The goal is to eliminate any space in the tank where condensation could form over the winter months. Moisture buildup can lead to water in your fuel, which can cause issues down the road. While the stabilizer helps prevent most of these problems, it’s always better to be safe and completely fill the tank.

Install Fuel Shutoff Valve

Before doing anything else, it's crucial to check whether or not your mower has a fuel shutoff valve. If it does, you are free to skip this step and move on to the next section. If it doesn’t, don't fret—the installation process is quick and easy. Fuel shutoff valves are inexpensive and can be found at any hardware, farm, or garden store as well as your local John Deere dealer. Here’s how to install one quickly and easily.

First, locate the fuel line running from your fuel filter to the pump, as shown below. You’ll want to install the shutoff valve in a section of the hose between these two points. Start by using clamps to pinch off the hose on either side of where you plan to cut to prevent the fuel from spilling out. Be careful not to leave the clamps on too long, as this could damage the hose. Once the hose is pinched off, use a pair of cutters to make a clean cut in the line. Be prepared with a rag for any fuel that may drip out at this step in the process.

Next, slide hose clamps onto both cut ends of the hose, then push the barbed ends of the shutoff valve into the hose, as shown below. After the valve is in place, move the clamps in close to the valve and tighten them down with a flathead screwdriver. Make sure they’re snug enough to prevent the hose from slipping off but not so tight that they damage the plastic valve.

With the valve securely installed, remove the temporary clamps and check for leaks. If everything looks good, you’re ready to move on to the final step.

Run Mower for 5 Minutes

Now that the stabilizer and gasoline have been added to the tank and the fuel shutoff valve is in place, the next step is to start and run the mower for five minutes to begin the mixing process. This ensures the fuel stabilizer reaches every part of the system, from the tank to the carburetor. When five minutes is up, DO NOT turn off the mower, but rather use the shutoff valve to stop the flow of fuel from the tank to the engine. The mower will continue to run, eventually burning through the remaining fuel in the lines and shutting off on its own. This step ensures no fuel is left in the carburetor to evaporate and potentially leave behind harmful residues over the course of the winter months. 

Once the engine stops running, turn the key to the off position with the knowledge that your mower is officially winterized and ready to be stored. This process helps protect your engine from the effects of stale fuel and prevents costly damage when you're ready to run in the spring.

NOTE: Fuel stabilizers can also be used for routine maintenance rather than winter storage. In this case, it's still considered best practice to run through all the steps outlined above for effective cleaning of your fuel system and to enure your mower stays in peak condition.