What Happens If You Put Old Gas In A Lawn Mower?

Last Updated on June 16th, 2023

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Nearly all lawn mowers run on gasoline, and let’s be honest – gas is not cheap these days. Your lawn probably needs a touch-up now, and you have a red gas can sitting in the corner of your garage. The gasoline it contains is old, can you still use it?

Utilizing older gasoline will not harm your lawn mower by any means. It might just not run as well as you might hope. So before that BBQ next Sunday, let’s discuss everything you need to know about using older gasoline with your lawn mower.

A black lawn mower on grass - What Happens If You Put Old Gas In it?

Will you be Able to Start a Lawn Mower?

Yes, you will most likely be able to start your lawn mower after filling its tank with older gasoline. However, it might take more time than usual and not run as effectively or smoothly.

If starting the engine on older gasoline does not work for you, you will likely have to remove the gas from the lawn mower or dilute it with fresh gasoline. Only do this if too much residue is built up within the gasoline canister.


What are the Potential Problems?

The biggest potential issue you may run into when using older gasoline in your lawn mower is sediment or residue buildup. Avoid these the best you can because they may prevent your entire lawn mower from running. See the list of potential problems below.

  • Sediments, residue, and other deposits can clog the lawn mower’s fuel lines and other components, preventing it from working.
  • If the lawn mower does start, you may find yourself mowing all day because the system might consistently quit or not work as well as before.


What if you Continue Using old Gas?

You might just be lucky if you do not run into any issues the first few times when using older gasoline in your lawn mower. However, if you continue to use the older gasoline in the lawn mower, you will absolutely run into more long-term issues over time.

There is bound to be buildup due to the older gas breaking down without being conditioned or treated. As a result, long-term use of older gasoline will likely result in an entire replacement of the lawn mower, if not the replacement of all major components.


How Can You Know If Your Gas is Old?

There are a few different things to consider when determining if your lawn mower gasoline is older. See the list below for things to look out for or consider when making this determination.

  • The gasoline has a much stronger aroma than it normally would.
  • The gasoline is darker in color, with visible residue buildup.
  • The gasoline is at least a month old.


How do you Treat Old Gas in a Lawn Mower?

There are many products on the market that can be utilized to treat older gasoline to ensure it will last a bit longer than usual. Aside from diluting the older gasoline with newer gasoline, listed below are some fuel additives/stabilizers to look into.

  • Sea Foam Motor Treatment – $12.99
  • STA-BIL Gasoline Fast Fix Small Engine Treatment – $6.99
  • B-ECO Fuel Tabs – $19.95


Final Thoughts on the Outcomes of Using Old Gas on a Lawn Mower

Using older gasoline on your lawn mower may or may not harm your lawn mower. It depends on how old the gasoline might be. The lawn mower is likely to start. However, you could run into some issues. Issues will be the result of gasoline with residue or sediment buildup.

If you continue to use older gasoline, you are bound to run into more issues that will likely result in the need to replace the entire lawn mower completely.

First, determine how old your gas might be if the smell is stronger than usual. There are products on the market sold to treat your old gasoline.

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