Can I Leave Gas in My Lawn Mower? (This Might Happen)

Can I Leave Gas in My Lawn Mower

You may be curious if you can leave gas in your lawn mower if you need to store it for a long period of time, such as during Winter. However, since gas is such a potent fluid, it may not be wise to do so. But, on the other hand, it may be beneficial. So, can you leave gas in a lawn mower?

Leaving gas in your lawn mower is perfectly fine. In fact, in some cases, it is suggested you leave a full tank of gas in your lawn mower. However, you cannot leave gas with ethanol in your lawn mower because the ethanol will clog up the motor, and the motor will stop working. 

There are other things to consider when deciding whether or not to leave gas in your lawn mower, including where you live, what additives are best in your gas when leaving gas in the tank, and how much gas you should or shouldn’t use. But don’t worry, we will cover all that.

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Here’s a Quick Pro Tip!

To ensure your mower is ready to be stored for winter, use a stabilizer or prepackaged gas with a fuel stabilizer already mixed. If you need to remove old gas first, use a turkey baster. 

Here are the products we suggest to ensure that your lawn mower is functioning optimally year-round:

1. STA-BIL Storage Fuel Stabilizer: This stabilizer was ranked the best by Consumer Reports. You can mix it with ethanol gas, and it lasts two years. It’s made specifically to store gas in a motor. 

2. STAR BRITE STAR BRITE Gasoline Additive: This is another good fuel stabilizer option. It eliminates dry start-ups and won’t turn into varnish. It will also extend oil and engine life and can be used in regular gas engines and diesel. 

3. Zulay (Large) Turkey Baster: It seems silly to use a turkey baster to drain out your gas tank, but it gets the job done. This baster is large and should aid in removing old gas faster. 

Leftover Gas

Depending on what kind of gas you leave in the lawn mower and how long you leave the gas sitting can be the difference between a working mower and a mower that’s better off being replaced. So, let’s talk about the options.

How Long Can You Leave Gas in a Lawn Mower?

You can leave gas in a lawn mower all winter if you stabilize the gas and make sure you do not use gas with ethanol. Even for weekly use, it’s best not to use gas with ethanol because the ethanol oil will separate from the gas and cause clogs.

To add stabilizer to the gas when you winterize your mower, you can either buy a bottle of stabilizer separately or buy pre-packaged gas and stabilizer.

If you plan to store your mower in a basement, then it’s best to drain all the gas instead because it’s a fire hazard. 

Can You Leave Gas in a Lawn Mower Over the Winter?

You can leave gas in your lawn mower over the winter if you use a stabilized non-ethanol gas and fill up the whole tank.  You can also winterize your lawn mower by completely draining the mower of gas and properly disposing of the gas after.

If you choose to store it in a basement, be sure to drain the gas instead. If you are storing it in an outdoor shed or garage, you can keep it full with stabilized gas. You can buy a stabilizer separately or premixed with gas. 

What Happens if You Leave Gas in a Lawn Mower?

If you leave gas in a lawn mower for an extended period and it contains ethanol, the gas will cause corrosion and clogs. Some lawn mower repairs are not worth fixing after ethanol gas is left in the lawn mower because the motor and valves might need to be replaced. 

If you don’t store the mower with a full tank of stabilized gas, the gas can create a varnish that will clog up the valves and filters as well. Also, if you store a lawn mower in a basement with gas in it, it can result in a bad house fire. 

Will My Lawn Mower Still Work if I Leave Gas in it Over the Winter?

If you use stabilized gas without ethanol and fill it up completely, you can store a mower with gas in the winter. However, if you are using gas with ethanol, you will need to drain the gas first before storing it for the winter. Otherwise, it will not work again in the spring.

The ethanol in your mower can cause a big problem if it’s left for too long. Over time, the oil will become too thick for the filter and valves.  If the oil cannot run through the motor properly, it will get stuck and stop working.

You might also enjoy our post on If Lawn Mowers Can Explode

How Long Before Gas Goes Bad in a Lawn Mower?

Gas can turn into varnish if only a little is left in the tank, which can clog the filters and valves. However, gas with ethanol can only last one to three months before the ethanol starts to separate and create clogs. Meanwhile, gas without ethanol can last three to six months.

If you add a stabilizer, the gas can last a year or longer.  It’s also important to properly store gas because it is combustible. It should be stored away from the house and in either a shed or garage.

It also shouldn’t be placed anywhere that is too hot, so make sure it’s not in the sun. 

Winterizing Your Lawn Mower

Unless you live in an area where grass grows year-round, you’ll need to winterize your lawn mower. However, this task doesn’t have to be difficult.

In fact, we’ll walk you through how to do it!

What is the Best Way to Winterize Your Lawn Mower?

There are two good ways to winterize your mower so it works great the following spring. The first way is to drain the gas from the tank completely. Another way is to fill the gas tank with stabilized gas and store it in a shed or garage separate from the main house.

If you use stabilized gas, you don’t have to worry about cranking it up in the spring. However, you should still check the oil, sharpen the blades, and change or clean the filters.

Also, check all of the electrical and replace the spark plug every 100 hours of use. 

Should I Use a Fuel Stabilizer When Storing My Lawn Mower?

You should use a fuel stabilizer when storing your lawn mower.  Filling your tank with gasoline and a stabilizer allows you to store it for a year or more.   If you don’t add a stabilizer, you can only store gas in a tank for three to six months. So it’s best not to start it up after more than a month without a stabilizer.

You can also store a lawn mower after draining the gas out completely. If you drain the whole tank, you can store it without worrying about it being a possible fire hazard.

However, if you use a fuel stabilizer, you can crank the lawn mower after months of not using it. 

What is the Best Gas Stabilizer For a Lawn Mower?

Consumer Reports ranked STA-BIL Storage Fuel Stabilizer as the highest gas stabilizer. This stabilizer claims to stabilize fuel for up to two years. STA-BIL also has a high-ranked ethanol treatment solution and prevention stabilizer. 

Two other highly ranked gas stabilizers are the PRI-G Fuel Stabilizer and the Lucas Oil Fuel Stabilizer. You can use this with ethanol-free gas after you drain out any ethanol gas, and the stabilizers will get rid of any residual ethanol. 

How Do You Use a Fuel Stabilizer in a Lawn Mower?

Simply mix one oz of stabilizer for every 2 ½ gallons of gas. Some stabilizers can be mixed with gas that contains ethanol, and they can last over a year to two years. For example, STA-BIL Storage Fuel Stabilizer lasts up to 24 months and can be used with gas with ethanol.

If you are unsure how much gas your lawn mower has, you can drain the tank and use the gas in your car. Otherwise, you will need to properly dispose of the gas using safe guidelines.

For example, you should not dispose of gas down the drain, in the trash, or on the ground.  

Forgot to Winterize 

If you forgot to winterize your lawn mower, and now it’s spring, and the grass is starting to grow, do not crank up the engine just yet! 

What Should I Do If I Leave Gas in My Lawn Mower Over Winter?

If you left ethanol gas without a gas stabilizer in your tank, you would need to drain the old gas and refill it with new gas that has a gas stabilizer in it. Do not try to crank it first! It’s also good to check the oil and filters and sharpen the blades before mowing the lawn. 

You shouldn’t mix new gas with old gas. If your oil is low, you can top it off without changing it, but the gas should be completely drained and refilled with stabilized gas, especially if it has ethanol. 

What Should I Do If I Forgot to Winterize My Lawn Mower?

You can drain the old gas and replace it with a new gas and fuel stabilizer. The proper ratio is one ounce of stabilizer for every 2 ½ gallons of gas. Then check your oil and either top it off or change it. 

When you are bringing your lawn mower out for the first time after the winter months, it’s a good time to sharpen the blades and clean or change out the filters.

Also, if you haven’t changed your spark plug recently, give it a change too. It needs to be replaced after every 100 hours of use. 

What Should I Do If My Lawn Mower Won’t Start After Leaving Gas in it?

If you have left gas in your mower for more than a month and it contains ethanol, the gas is now stale and needs to be drained of what’s left and replaced with new gas. You should also add a fuel stabilizer as well. 

If your lawn mower will not crank after changing the gas, take a look at the oil and either top it off, or change the oil. Also, check the filters and spark plug.

If it still does not come to life, take your lawn mower to the shop. In some cases, a new mower is best.

Can I Mix Old Gas with New Gas?

It’s not good for a motor to mix old gas with new gas. Old gas often has turned into varnish, which can clog up the valves and filters. It’s suggested to drain the gas out completely before filling it up with new gas.

It’s also a good idea to add a stabilizer to the gas tank to get rid of any ethanol that clogged up the valves. So the next time you store your mower, fill the tank with stabilized gas. That way, you won’t have to change the gas in the spring. 

How Long is Gas Good for in a Gas Can?

Most gas has a shelf life of up to three months. If it’s stabilized gas, it can last a couple of years. Gas with ethanol and without a stabilizer only lasts up to one month. It’s important to store gas in a place that’s not in direct sunlight because it is highly combustible. 

It’s also not safe to store a can of gas or a motorized engine with gas in a house or an attached basement. You should drain a vehicle’s gas tank before storing it in or around a house. Storing it in a shed or separate garage is good. 

You might also enjoy our post on Do Lawn Mowers Take Regular Gas?

Related Questions

How Long Will a Lawn Mower Run on a Tank of Gas?

The time it takes to run on a tank of gas depends on the mower, but on average, it takes about 2 ½ hours of mowing to use up a tank of gas. This is for standard push mowers and small riding mowers.

If you are not using stabilized gas, make sure you are circulating the gas in the tank, using it every week, and refilling it with new gas often.

If you are using gas with ethanol, you will need to change out the gas every month at the very least. 

What Is The Best Type of Gas for a Lawn Mower?

Lawn Mowers use the same type of gas regular cars use. The best additive for a mower is a stabilizer. A stabilizer extends the shelf life of the gas, which is helpful when you are storing your mower more than you are using it.

Other motorized appliances might use different gas. For example, snowblowers use a different type of gas you can’t get at a normal gas station. If you are ever in doubt about what type of gas a motor needs, read its owner’s manual. 

Final Thoughts

I hope you read this article before you stored your mower away, but if not, you might still be able to revive it without having to replace anything. Just remember to drain the old gas and put in new stabilized gas before cracking it up.

Finally, I hope you have a lovely upcoming summer and can enjoy your freshly mowed grass. 

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