Hook: “Spring is in the air, and your lawn is calling for attention – but what if your gas-powered lawn mower has been sitting with last season’s old fuel in its tank?”
Mini-hooks:
- Break down of old gasoline
- Impact on lawn mower engine performance
- Formation of gum-like residue on key components
- Mixing old and new gas in your lawn mower
- Importance of draining the fuel tank before storing
Atomic Facts:

- Gasoline starts to break down after 30 days
- Old gas can gum up and form a varnish-like layer on carburetors, fuel lines, and injectors
- Mixing old and new gas can leave deposits behind and cause rough starts
- Fuel stabilizers can slow down the oxidation process, but fresh fuel is still the best choice
- Draining the fuel tank before storing can prevent damage to your lawn mower
This Is What Happens When You Use Last Season’s Gas In Your Lawn Mower
The Breakdown of Old Gasoline
Gasoline starts to break down after about 30 days, which means that if you’ve stored your lawn mower for an extended period, its fuel tank may contain old, stale gas. This is a problem because old gas can cause issues with your lawn mower’s engine performance.

Impact on Lawn Mower Engine Performance
When gas breaks down, it doesn’t merely dissipate into thin air. Instead, it gums up and forms a filmy, varnish-like layer of debris on key lawn mower components like the carburetor, fuel lines, and injectors. This residue can prevent your mower’s engine from starting, clog the carburetor, and even potentially damage the fuel system.
The Dangers of Mixing Old and New Gas
If you break out your lawn mower to discover it’s sitting with just a little bit of fuel, it might be tempting to put new gasoline in and get mowing with a mostly fresh tank. Unfortunately, that’s not the best idea, either. Mixing old and new gasoline may “freshen” things up, but you’ll still be running your lawn mower on degraded fuel, which can leave deposits behind and potentially cause rough starts or running issues.

Why Draining the Fuel Tank Before Storing is Important
To avoid gasoline-related issues with your lawn mower caused by old, broken-down fuel, you should drain your mower’s fuel tank completely before storing it for long periods of time. This will prevent the buildup of gum-like residue on key components and ensure that your mower is in good working condition when you’re ready to use it.
The Benefits of Fuel Stabilizers
If you’re hoping to make your gas last longer, there is one alternative: add a fuel stabilizer. These additives can slow down the oxidation process, helping your fuel last for as long as 12 to 15 months. As you prepare to store your lawn mower, you can drain any leftover gasoline and fill the tank with freshly stabilized fuel. However, it’s essential to remember that fresh fuel is still the best choice.

The Risks of Using Last Season’s Gas
Using last season’s gas in your lawn mower can lead to issues such as:
- Hard starts
- Poor engine performance
- Clogged carburetors
- Damaged fuel systems
Best Practices for Storing Gasoline- Powered Equipment
To keep your gas-powered lawn mower in good working condition, follow these best practices:
- Drain the fuel tank completely before storing
- Add a fuel stabilizer to slow down the oxidation process
- Use fresh fuel when you’re ready to use the mower
- Keep the mower in a well-ventilated area to prevent the buildup of stale air
Conclusion
Using last season’s gas in your lawn mower can cause damage to your equipment and lead to issues with engine performance. To avoid these problems, it’s essential to drain the fuel tank before storing and use fresh fuel when you’re ready to use the mower. By following these best practices and using a fuel stabilizer, you can keep your lawn mower running smoothly and extend its lifespan.





