Should You Drain the Gas From Your Lawn Mower Before Winter? Here's What Experts Say

Just like the groundhogs and other woodland creatures, your lawn mower likely hibernates in winter. For most climates, it won’t be necessary to mow your lawn during these months, when grass slows its growth or goes completely dormant, and exposure to the cold can damage your mower. But before the frost and snow set in, you'll want to be sure to safely store your lawn mower and protect it from the elements.

After the mowing season, your lawnmower’s fuel tank might still be partially full—so what should you do with that fuel? Is it safe to leave it in the tank until spring, or does it need to be drained? We consulted lawn care specialists to determine the best course of action for disposing of the fuel left in your lawnmower’s tank before storing it for winter. 

How Old Fuel Affects Your Lawn Mower's Tank

Whether you forgot about fuel in your lawn mower's tank or the first frost takes you by surprise, it is generally not recommended to leave old fuel in the tank while stowed away. "If old gas sits in your mower all winter, it starts to break down and form varnish-like deposits," explains the founder of Lawn Guru, Skye Durrant. "That sludge clogs the carburetor and fuel system, which often leads to hard starts, sputtering, or a complete failure to start in spring."

That fuel degradation can begin to occur within just 30 days. And in the worst cases, you might need to rebuild or replace parts of the fuel system—a costly and time-consuming task, adds Durrant. 

Proper Storage of Your Lawn Mower's Fuel Tank

To keep your lawn mower’s internal components safe from harm during the winter, Durrant recommends either draining your lawn's mower's tank by running the mower until it’s completely out of gas, or filling the tank with fresh gas plus a fuel stabilizer and letting it run for a few minutes to cycle it through.

Both are legitimate practices, and both have their benefits and drawbacks. "Some people prefer to use stabilizers, rather than try to drain the tank themselves," explains lawn care specialist Chrissie Handley, "as you can run the risk of leaving some fuel behind and not draining it completely.” Additionally, conserving fuel for the next mowing season is often considered more cost-effective.

Pros and Cons of Draining Fuel vs. Using Fuel Stabilizer

You'll want to take care of your lawn mower to the best of your ability, both for its longevity and to keep it running smoothly.

Before deciding which method is best suited for you and your lawn mower, consider the following pros and cons of each as laid out by our lawn care experts.

Draining the Fuel

• Pro: Draining the fuel eliminates the risk of stale gas. Without stale gas, there is no chance of buildup in the fuel system, explains Durrant.
• Pro: Minimizes the risk of any unwanted moisture inside the tank, which can cause corrosion if you’re storing it away for a few months.
• Con: Mowing your lawn long enough to run out of gas can be time-consuming. Alternatively, using a hose or a siphon pump to remove any spare fuel from your mower and transferring it to a fuel-safe container can also be a messy and arduous process.
• Con: According to Durrant, draining the fuel leaves rubber seals and gaskets exposed to air, which can dry them out over time.  

Using a Fuel Stabilizer

• Pro: This method is great for people looking for an easier solution, says Durrant. It's typically a quicker, cleaner process.
• Pro: The fuel stabilizer protects the engine during the cold months by keeping fuel system parts lubricated.
• Con: There is more of a margin of error with this option. Using fresh gas, the correct amount of stabilizer, and running the engine to circulate it is required. “You have to fill the tank and run your mower for a while after adding the stabilizer to make sure it circulates through the entire system,” explains Handley.
• Con: The tank needs to be newly filled in order for the stabilizer to work properly, according to Durrant. Adding a fuel stabilizer to old gas will not help.
• Con: Stabilizer is not ideal for long-term storage. “A stabilizer can be a good short-term solution for seasonal storage, but isn’t really recommended if you’re looking to store your mower for over a year or two,” explains Handley.