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Is it OK to Leave Gas in Mower Over Winter?

By Jeff Mercer · Updated September 24, 2026 · 3 min read
Is it OK to Leave Gas in Mower Over Winter?
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Hey there, it’s your pal Jeff here. I’ve had my share of winter mowing mishaps, and one question I get asked a lot is whether it’s okay to leave gas in the mower over the winter.

Well, read on and I’ll fill you in on what you need to know.

Why You Shouldn’t Leave Gas in Mower Over Winter

First off, let’s talk about why you shouldn’t leave gas in your mower over the winter. Gasoline is made up of a bunch of different chemicals, and over time, these chemicals start to break down and form gunk and contaminants.

This process is accelerated by heat, moisture, and air exposure, so if you’ve got a tank full of gas sitting in your garage all winter, it’s likely to go bad faster than a tank that’s been emptied and refilled with fresh gas.

Leaving old gas in your mower over the winter can cause all kinds of problems, including engine damage, poor performance, and difficulty starting.

And if you’re not using your mower during the winter months, it’s likely that the gas will go stale before you even have a chance to use it again.

What to Do with Gas in Mower Over Winter

So, what should you do with the gas in your mower over the winter? Here are a few options:

  • Drain the gas out of the tank and refill it with fresh, high-quality gas before storing your mower for the winter.
  • Add a fuel stabilizer to the gas to help extend its shelf life.
  • Store your mower in a cool, dry place to help prevent the gas from going bad.

FAQ

Is it OK to Leave Gas in Mower Over Winter?

It’s generally not a good idea to leave gas in your mower over the winter.

Gas starts to go bad after about three to six months, and leaving old gas in your mower over the winter can cause all kinds of problems, including engine damage, poor performance, and difficulty starting.

Can I Add Fuel Stabilizer to Old Gas in Mower?

Yes, you can add fuel stabilizer to old gas in your mower to help extend its shelf life.

However, keep in mind that fuel stabilizer is not a permanent solution, and it’s best to drain and refill your mower with fresh, high-quality gas before storing it for the winter.

Can I Store My Mower Outdoors Over Winter?

It’s generally not a good idea to store your mower outdoors over the winter, especially if you live in an area with extreme cold or moisture.

Cold temperatures can cause the gas to thicken and become difficult to start, and moisture can cause rust and corrosion. If you must store your mower outdoors, try to find a covered area and add a fuel stabilizer to the gas to help extend its shelf life.

Conclusion: Don’t Let Your Gas Freeze

In conclusion, it’s important to pay attention to the age of your gas when using a lawn mower (or any other gas-powered equipment).

Gas starts to go bad after about three to six months, and using old gas can cause all kinds of problems, including engine damage, poor performance, and difficulty starting. If you’ve got old gas in your tank and you’re not sure if it’s still good, it’s best to drain it out of the tank and refill it with fresh, high-quality gas.

And if you need to store your mower for the winter, make sure to follow the tips above to help extend the shelf life of the gas.

So, remember, don’t be like me and end up with a frozen mower and a whole lot of snow to shovel. Keep your gas fresh, and you’ll have a smooth, hassle-free winter.

Happy mowing (or shoveling)!

Before you start the repairWe are not certified small-engine technicians. Before any repair, pull the spark plug wire and let the engine cool. Anything involving blades under a raised machine, fuel system leaks or transmission internals — if you're not sure, have a dealer or small-engine shop look at it.

Written by

Jeff Mercer

Jeff Mercer writes GardenTooly's answers to the questions people type into a search bar while standing next to a machine that won't behave: why the deck shakes, why the mower dies when it warms up, whether a bent blade shaft can be straightened, what the difference between two transmissions really means for you, and which fuel additive is worth the shelf space.

Each answer starts with the cause that is most likely and cheapest to check. Where it comes from the owner's manual, a service bulletin or what owners report, it says so, and anything involving blades, fuel, a jacked-up machine or a hydrostatic transmission gets a plain "take it to a shop" when that's the right call.

A note on our names: GardenTooly is written by a small team under pen names, one name for each job, and Jeff Mercer is the name on our mower and small-engine guides. We are not certified small-engine technicians, and we don't sell equipment.