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How to use fuel stabilizer in a lawn mower

Is a fuel stabilizer necessary for lawn mowers?

One of the things you will need to consider when buying gas for your lawnmower is whether you will have to add fuel stabilizers.

Some lawn mower owners consider it a must-have for their machines, while others don’t deem it necessary.

The use of stabilizers depends on how you intend to use your lawnmower. For example, stabilizers are unnecessary if you use fresh gas that you don’t plan to store.

However, if you plan to store gas for future use or leave it sitting in your lawnmower gas tank for long, you should use stabilizers.

Fuel stabilizers are easy to use; you must add them correctly to your lawnmower gas. We have compiled important information about the stabilizers in lawn mowers, from their benefits to the best way to use them.

What is the benefit of using a fuel stabilizer in a lawn mower?

Fuel stabilizers are solutions that are added to fuel to protect it from degradation. The degradation occurs when the fuel is left sitting in the lawnmower tank or your gasoline canister for a long time.

Lawnmower gas degradation occurs in several ways, such as:

  • Evaporation – some lighter hydrocarbons and ethanol in gas can evaporate, leaving stale fuel that is harder than usual.
  • Absorption of moisture – ethanol in gasoline is hygroscopic and can absorb moisture over time. The humidity can cause engine damage.
  • Oxidation – compounds in the gasoline react with oxygen in the air forming solid substances commonly referred to as gum.
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Adding fuel stabilizers to gasoline provides an extra layer of protection, preventing oxidation, evaporation, and moisture absorption.

As a result, the shelf life of the fuel is improved from around one to six months to as long as one to three years.

Can you use a fuel stabilizer in a riding lawn mower?

You can use fuel stabilizers on all lawnmowers, from handheld to riding lawnmowers. In addition, you can use stabilizers with 2-stroke engines, which use gas and oil.

Fuel stabilizers are not limited to lawnmowers; you can use them on all types of engines, including gasoline and diesel engines used in other machines and vehicles.

Change lawn mower oil
Image: Tony

How much fuel stabilizer should you use?

Like every other fuel additive, you must mix your gas and stabilizer in a specific ratio. So, how much fuel stabilizer per gallon of gasoline should you use?

The mixing percentage varies from different stabilizer brands to others. For example, one of the most common stabilizers for lawn mowers – STA-BIL 360 Protection – recommends around ounces per 2.5 gallons of gas.

Other fuel stabilizers will have different mixing ratios, which can be higher or lower. But, again, the ratio depends on the stabilizer’s brand and not the engine type of the machine you are using.

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However, the ratio can be affected by the type of gasoline (such as oxygenated or ethanol percentage) and whether it is regular or mixed (with oil) gas.
Therefore, you should always consult the fuel stabilizer packaging for the proper mixing ratios.

Can you use too much fuel stabilizer in a lawn mower?

What happens if you use more than the recommended mixing ratio of the fuel stabilizers? The effect on the engine will depend on how much more stabilizer you have used.

If you have added just a little more than the recommended, there won’t be any significant effect.

However, too much stabilizer can dilute the gas since the solution mixes thoroughly. When this happens, you will have problems running your lawnmower engine.

For example, the engine might refuse to start, start leaking, produce a lot of smoke, or even fail. And since adding too much stabilizer doesn’t offer any significant benefits, you will be just wasting money while risking damage to your lawnmower.

When should I add a fuel stabilizer?

To get the best out of your fuel stabilizer, you should only add it to the gas when it is fresh. The best time to add it is when filling up your gas canister.

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Pouring the stabilizer before filling the gas will allow it to mix thoroughly, thus offering the best level of protection.

You can still add a fuel stabilizer to your gasoline later on, for example, when adding it to the lawnmower gas tank.

However, you should not add a stabilizer if your fuel has been sitting for more than 30 days – it will already have started degrading and will not offer significant benefits.


Adding a fuel stabilizer is the best way to increase the shelf life of your fuel and avoid many issues that can affect your lawnmower engines.

It thus comes in handy when planning to store lawn mower gas or leave it sitting in the fuel tank, for example, over the winter.

However, there are a few things to consider with fuel stabilizers. First, you can only use them with fresh gas; otherwise, it will not offer much protection.

Secondly, you should follow the correct mixing ratios, as using too much stabilizer can dilute the fuel, causing issues with your engine.

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