Lawn Mower Storage: Why Draining The Fuel Tank Is A Mistake

How to winterize a lawn mowerWondering how you can ensure your lawn mower and outdoor power equipment will be ready to roll when the grass turns green?

If you’ve checked your manufacturer’s guide, you’ve probably seen a suggestion to perform some preventive maintenance prior to storage. This is always a good habit to get into. Some manufacturers will also recommend running your equipment dry before putting it away for the winter.

While draining the fuel tank may sound like a good idea, it could harm your engine.

Running a lawn mower dry will make it harder for it to fire right up when it comes time to take it out of storage. This is true of all your outdoor equipment and tools, from mowers and blowers to trimmers and chainsaws.

Lawn equipment relies on three basic elements to work. If you don’t have all three, your engine will not run:

  1. Air
  2. Spark
  3. Fuel

Clean air will always be available if you take time to clean or replace your air filter. And a clean, properly-gapped spark plug usually takes care of the spark.

But fuel? If you don’t maintain components that help properly distribute gas at the right time and in the right amount, your equipment might not perform well. In fact, it may not run at all.

Draining the tank harms your lawn mowers carburetor

Draining the tank harms the “heart” of your equipment. Think of one of the most important organs in your body: your heart. The lawn mower carburetor is, in many ways, your engine’s “heart.” It blends air and fuel and circulates these elements into an engine’s cylinders.

Each time you drain the gas tank, you inadvertently put stress on your equipment’s critical “organ.” Here’s what happens:Lawn Mower Carburetor

  • Draining fuel allows oxygen to enter the lawn mower’s carburetor.
    It’s impossible to get every last drop of gasoline out. When oxygen attacks the small fuel droplets left behind, it causes gum and varnish. If this debris settles in the wrong place, such as a needle valve tip, the carburetor will need cleaning to work properly.
  • Where there is air, there is water (damage).
    Allowing your gas tank to sit empty for long periods leaves a huge area for water vapor to condense. When moisture collects, it can trigger corrosion in the tank, fuel lines, carburetor and cylinders, and can even cause catastrophic engine failure if a big “gulp” is taken into the engine all at once. (If your mechanic says there is “white rust” in the carburetor, this is why.)
  • Fuel system plastics and rubbers are designed to live in fuel.
    These parts can become brittle and crack when exposed to air.

What to do instead: Avoid risks with gas stabilizer.

Winterize lawn mowers with STA-BIL Manufacturers sometimes recommend draining the tank to winterize a lawn mower because the worst thing you can do is leave old fuel in an engine during long periods of storage.

You may have followed this advice in the past without noticeable issues, but that doesn’t mean you’re in the clear. If draining the tank becomes a yearly habit, there’s a good chance you’re shortening the lifespan of your lawn mower and other tools, and may accidentally put your family in danger.

There’s a much easier way to properly store your lawn equipment. To avoid damage, simply use a quality fuel stabilizer and fresh fuel before putting equipment away for the season.

Here’s how to winterize a lawn mower correctly

Step 1: One month before the end of the season, start putting fuel stabilizer in every gas can.
This is an easy way to provide some basic protection for your engine, even if you forget the next three steps.

Step 2: Buy and stabilize fresh fuel for maximum protection.
Adding fuel stabilizer to old fuel will stop it from degrading further, but the fuel may already have broken down.

Step 3: Fill your tank 95% full with fresh, stabilized fuel.
Leaving a little room prevents the fuel from expanding and spilling in warmer weather, and reduces the risk of water vapor that can condense and contaminate fuel.

Step 4: Run the engine for a couple of minutes.
This gets the stabilized fuel into the carburetor and fuel lines.

That’s it!

While you should still consult with your manufacturer for product-specific equipment and engine maintenance tips, these simple steps apply to all engines, big and small. A few minutes on each piece of yard equipment can save hours when the grass starts growing and the season kicks off in spring.

Join the Conversation

Your email address will not be published. Required fields are marked *

  • step one is incorrect. an ethanol treatment should be used all of the time. oxygenated fuel @ 10% (e10) adds 3 1/2% oxygen to the fuel and oxygen contains water which can cause “white rust” (calcium and lime) it also enleans the fuel to a mixture from 14.7 to 1 to 15.2 to 1. which can increase the engines running temperature.

    • We recommend treating the fuel as soon as it is dispensed from the pump This will ensure that the fuel will be kept as fresh as possible and also help keep the fuel system clean. There is no need to add any more STA-BIL® Brand unless more fuel is added. In such case, simply add enough product to cover the additional fuel. If the concern is countering the negative effects of ethanol in the fuel system, we highly recommend treating with STA-BIL 360® Performance™, which will prevent such issues such as corrosion, rust and condensation issues. It will also stabilize fuel for at least 12 months. Please contact us at if you have any questions about this. Thank you.

  • On step 4 when said to run with fuel stabilizer for couple minites, then do we still leaved fuel stabilizer in tank thru winter?

    • Hi Larry, after adding fuel stabilizer to a full tank and letting the engine run for a few minutes, then you are done. That’s all you need to do! Please contact us at if you have any questions.

  • I have been doing the same thing with all my gas power equipment since 1976 . [ snowblower, chain saw , gas trimmer , gas power washer, gas power generator , my John Deere lawn tractors right up to my new 2017 X – 570 JD . Just add a bottle of dry gas [ STA – BIL ] Starts right up come spring time. I run that same gas for my 1st lawn cutting then just had fresh gas to the tractor. Never had one single problem.

  • Thanks for the information

  • What if it is already January,.. and quite cool,..
    (2 degress C at night), ….and I CANNOT start my mower and weed eater easily..?
    Should I just pull the cord to distribute gas and stabiizer?

    • This will not get the gas into the carb. The carb bowl can be remove and let the fuel run through and then replace. Please contact us at if you have any questions about this. Thank you.

  • I am new at this and just learned this information. My mower has some gas left in it, and today is the first warm day we’ve had, so I went and bought some stabilizer. Can I put it directly in my tank with the gas it already has left in it and run the mower before storing it for the rest of the winter? I live far from town and don’t think I am able to go get fresh fuel. Thanks!

    • Yes. It goes directly into the mower’s gas tank. Although it is best to keep the lawnmower’s tank as full as possible prior to storage, treating the remainder fuel with STA-BIL and running the engine for about 2 minutes will help in keeping the system from varnishing (gunk).

  • I have tried all ways to store my snow blower for the summer and have still replaced the carberator several times. I now have found the answer. I use Tru Fuel available at Home Depot And Lowes. It is gasoline with NO ethanol. I still use stabil and still drain the tank and carb before storage. Been several years now with not one problem. Yea, it’s 20 bucks a gallon but how much do you use a season, maybe two gallons. Less that a carberator

    • You are correct. It is definitely true that non-ethanol fuel is more reliable than ethanol-blended fuel as it is not as susceptible to condensation, corrosion and rust issues and treating with STA-BIL still must be done to keep it as fresh as possible. However, if obtaining non-ethanol fuel is a challenge (cannot find it or unaffordable), we recommend trying STA-BIL 360® Performance as it tackles those problems while in use and storage.

  • Sounds like a good idea. I used 360 stabil and pure gas during the season. For me, the gas went bad and made the mower difficult to crank and keep running after about 6 weeks of nonuse. I’ll go back to running it empty at the end of the season.

    • We are disappointed to hear that our product did not live up to your expectations. There are several reasons that may affect results in storing fuel –from age and quality of the fuel, to the products shelf life (2 years after opening), to storage conditions. So far, in 60 years we have had very good feedback from consumers and STA-BIL is even recommended by many OEMs such as MTD and Generac as well as featuring a Full Satisfaction Guarantee. Having said that, dry storage is also a good option as long as it is done properly as leaving any residue in the fuel system may lead to varnishing, sediment accumulation, corrosion and rust.

  • Does fuel stabilizer ever get to old that it should not be used?

    • Hi Wayne, all STA-BIL products have a shelf life of two years from the time of opening. Unopened it’s 8-10 years. Please contact us at if you’d like help checking the manufacturing date of your bottle.