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Does lawn mower gas go bad in the winter?

When you have a gas lawnmower, you will use it the last time in the fall to cut it before the chilly weather arrives. Then you will store your mower for the winter and start using it again in the spring. But when you store it, you usually will still have some gas left in your tank. Is this a problem?

Does lawn mower gas go bad in the winter?

Yes, gas in your lawnmower goes bad in the winter when you do not use your mower. If gasoline is left in any small internal combustion engine, like a lawnmower, snowblower, pressure washer, chainsaw, or leaf blower, for more than three months, it will expire. As soon as the gasoline in your lawnmower reaches its expiration date, it can make your machine run poorly or even damage it.

(CC BY 2.0) by Dane Van

Scroll on to read the details about bad gas in your lawnmower.

What damage can a bad gas do to my lawnmower?

There are four major problems that bad gas will do to your lawnmower when it sits for more than three months unused during the winter season:

– Not starting

Your lawn mower’s small internal combustion engine will not start at all when you try it during the summer season. Bad gas has the potential to ultimately damage the inner parts of the carburetor of your lawnmower. Bad gas also can eventually damage your lawnmower’s fuel lines and seals.

– Run bad

Your lawn mower will not run as smoothly as it used to when you first bought it. Gasoline, when it expires, will turn into a varnish-like thick and greasy substance that can clog up the small fuel ports of your lawnmower, thus preventing it from starting and running smoothly.

– Sputter

Your lawn mower’s small internal combustion engine will sputter when you are using it.

– Keep dying

Your lawn mower will keep dying again and again while you are trying to operate it.

All these problems can lead to a waste of time and money. You may even have to repair or replace your lawnmower if things get bad.

What should I do if the gas in my lawnmower goes bad?

If your lawnmower is not starting and the reason is the presence of bad gas inside it, you must at once seek the assistance of a professional mechanic who will help you remove the built-up residue of the bad gas because it is choking the small internal combustion engine of your lawnmower. The bad gas you left inside your lawnmower tank throughout the winter months should now be siphoned out to get it started and running again. The second thing that the professional mechanic will help you find is the quantity of bad gas inside the tank of your lawnmower.

If siphoning out the built-up residue of the bad gas does not help the small internal combustion engine start again, you will have to remove the carburetor and clean it. Sometimes the condition of the carburetor is beyond cleaning, so you will have to replace it.

To avoid this headache, you must carefully mark the date and time when you added the gas to your lawnmower, along with a reminder that notifies you when to drain it out before winterization. Before storage, you must take your lawnmower to a recycling center and dispose of the gas properly in a safe place where it will not catch fire.

Why does the gas in my lawnmower go bad?

Ten years ago, the gas used for small internal combustion engines never used to go bad. The Environment Protection Department (EPA) has added ethanol to gasoline; this is why it expires within two months of sitting idle. Ethanol is a type of alcohol that is derived from maize.

87 Octane gasoline has 10 percent ethanol added to it to make it more environmentally friendly. The addition of ethanol makes gas cost-effective and more affordable, but it is harmful to the engines of your lawnmower, snow blower, leaf blower, chainsaw, and pressure washer. Ethanol can draw the moisture out of the air and water down your gas inside the tank of your lawnmower.

Gasoline that has ethanol added to it, whether stored in a can or inside the tank of your lawnmower or other equipment, goes bad and loses its volatility in as little as 30 days.

How to prevent the gas in my lawnmower from going bad?

When the summer season is coming to its end, you must fill the tank of your lawnmower with just as much gas needed to run the lawnmower for one last mow, mulch, or shredding job. Once you have completed your task, let your lawn mower’s engine run for as long as it stalls on its own. In this way, you will be 100% sure that all of the gas in the tank of your lawnmower has finished.

Now you must try to start the engine of your lawnmower once again. If the engine starts, it will burn out the few drops of gas that could not get burnt out in the last run. Before you plan to winterize your lawnmower, you must add a fuel stabilizer to its tank.

You must carefully read the instructions given on the package of fuel stabilizer, and you can also consult the owner’s manual of your lawnmower for further details. You must add the correct amount of the fuel stabilizer depending on the size of the fuel tank of your lawnmower. After adding the fuel stabilizer to the fuel tank of your lawnmower, you must run it for a few minutes to allow the liquid to circulate freely throughout the carburetor of your lawnmower.

Now you can turn off your lawnmower and winterize it without any worries. Even if you store it for more than six months, you can start it smoothly in the next spring season. Some excellent fuel stabilizers can increase the storage time to 24 months.

Three significant factors impact the storage time of your lawnmower:

  1. Location: The place where you want to winterize your lawnmower,
  2. Temperature: The temperature of the place where you want to winterize your lawnmower and
  3. Condition of the tank: The fuel tank of your lawnmower or the state of the container where you want to store the gas.

How do I know if the gas in my lawnmower has gone bad?

One of the simplest methods to diagnose if the gas in your lawnmower has gone bad or not is to smell it. Bad gas has a powerful and unpleasant smell as compared to fresh gas. As soon as you open up the cap of your lawnmower’s fuel tank and sense a sour smell, you must understand that the gas has now oxidized, and it is harmful to your lawnmower’s engine.

The second method is to drain the gas from the fuel tank of your lawnmower into a transparent plastic or glass bottle. If the color of the gas is now darker than when you first added it, it means that the gas has gone bad and is not usable anymore. Fresh gas has a light brown to golden color, while old gas turns into a dark chocolate color.

How do I look after the oil filters of my lawnmower?

You must regularly change the oil and the oil filters of your lawnmower. This way, you will be able to keep the moving parts of your lawn mower well-lubricated and remove small unwanted particles from your lawnmower’s engine. So you will be able to utilize the complete lifespan of your lawnmower’s small internal combustion engine.

You must regularly clean and replace the oil filter of your lawnmower and other small equipment because it keeps the dry grass and dry leaves out of your lawnmower’s engine. A clean oil filter is responsible for increasing fuel efficiency and the power of your lawnmower. There are two types of filters used in your lawnmower:

  1. foam filter
  2. paper filter.

If you are using a foam filter in your lawnmower, you must wash it after use with a bucket full of hot water and a mild non-toxic household detergent dissolved in it. After washing, you must squeeze it and allow it to dry thoroughly. Then, you must lubricate it in a thick layer of oil before re-installing it in your lawnmower.

And if you are using a paper filter in your lawnmower, you must replace it after each use. This is good for the health of your lawnmower.

Final Remarks

To summarize this blog post, I want to say that, YES, the gas in your lawnmower goes bad if you leave it unused for 3 to 6 months. To prevent this, you must dispose of it at a recycling center before you plan to store your lawnmower. You must also use a good quality fuel stabilizer; otherwise, the bad gas will clog up the fuel lines of your lawnmower.