The Secret Reason For Why There Is A Sponge In My Gas Tank!

If you’ve just bought a new lawnmower, there is a chance that there is something like a sponge in the gas tank. The sponge-like foam is specially fitted into your gas tank for different reasons among which is the safety of its users.

It is not uncommon to find foams inside newly built [engine’s] gas tanks, including lawnmowers. Most 5HP Briggs engine comes fully fitted with this foam-like materials.

If your lawnmower is the old type, this ‘sponge’ might not be there but having seen many recent versions of garden machines, the ‘spong technology’ is very visible when you look very closely.

So what is the purpose of this sponge in the gas tank?

There have been a series of questions from users who wanted to clean up their mowing device and discovered this spongy-look-alike material hanging somewhere in their gas tank. While some wanted to know the needs of this ‘sponge’ others have put a guess as to what it might likely do.

Whatever the role the sponge does in a tank, this informative guide is all that you need to know why it’s important to have a sponge in a tank and how to take care of it.

Reasons Why There Is Sponge In The Gas Tank

Gas tank sponge is no new thing. These foam-like materials have been in use on high-performance applications for many years, the only thing about it is that not many people knew that it can be a part of garden appliances so soon.

Here are the possible reasons why there is a sponge in your gas tank


This slosh or sloshing is not new to car racing – foams are placed inside a car gas tank so that it keeps the car ‘gas fluid’ balanced and stops it from causing fire during an accident. The foam is fitted to soak up the gas in the tank so there won’t be a spillover in case of sharp turning and sometimes car somersaulting.

In a lawnmower, the same process applies – the sponge keeps the garden tool’s [gas tank] balance and keeps the gas from sloshing around during heavy use. Without the sponge in the gas tank, the gas will likely wobble around, however; the foam is the only pressure inside the gas tank that keeps the gas in place. It’s a device put in there so that the performance of the lawnmower can be impactful.

Keep The Gas Intact

In some cases, the lawnmower could have become old due to heavy use – year after year and the components might be in rust including the gas lid. In such a situation where the engine is turned and twisted to spruce the garden, gas might escape from the tank and splash out but if there is a sponge in the tank it immediately soaked up the liquid from venting out.

There were lots of cases of stationary engines vibrating and gas splashing out of the tank lid. In most of the cases recorded, it had resulted in people thinking there is a defect with the tank lid and so had filed for complaint of a defective gas cap.

So the sponge in the gas tank act as a bridge to stop the gas from spilling out of the tank.

Fire Hazard

Another important reason there is a sponge in the gas tank is to keep the equipment from exploding. Gasoline and fire can cause untold damage wherever they occur. With the sponge inside the gas container, it’s very likely that gas spillage to cause havoc is drastically reducing. 

For instance, if you tossed a match inside a container with gasoline, the explosion will happen before the matchstick actually hit the gasoline.

The same way, when you place water in a cup, to the ordinary eye, it seems the water is down at the bottom while air is on top. However, the reality is that there are water molecules from the water escaping into the air while at the same time, water molecules from the air condensing back into water.

What this means Is that the sponge is fitted inside the gas tank to absorb the gas molecules escaping so it will not spill (per se) at the exact moment it get close to anything that can cause a fire.

Now that you know what these sponges do in a gas tank, do you still think it’s necessary to pull them out next time you are cleaning your gas tank? 

It’s no secret that some people say there is no significant difference in the performance of the device with or without the sponge.

Whatever the case, after a long while, the sponge will lose quality due to soaking alcoholic based content and so the debris or breakaways from the sponge might cause your gas tank to malfunction. 

However to prevent such happening and make sure the sponge stays strong you need some basic understanding of how to care for the gas tank…this is where the sponge is housed.

Here are some tips on caring for your gas tank that will prolong the lifespan of the sponge in the tank.

How To Care For Your Gas tank

If your lawnmower is laid idle for a long period, it may fail to fire up the next time you need to spruce up the yard. Many factors could make these gas pumps fail. Gas filter pumps clogged with contaminants and loose debris including rust can cause this failure.

Over time, the sponge in the gas tank can start to disintegrate. This can also cause it and it will make your gas filters to clog with foamy substance. 

Follow these tips to keep your garden device safe and running well:

  • Check up the sponge in the gas tank at least once in 3 months
  • Observe if the foam is disintegrating by pinching it to see if it will brittle and breaking apart.
  • Don’t keep gas in the tank for a long period.

What determines the longevity of your sponge in the gas tank [so the machine can continue to perform at its peak] depends on the type of gas you use. If you are using gasoline, your device might be able to make it to 5 years before you start needing to worry about your gas tank and if you run other alcohol based gas, the timeframe could be less.

The single most important way to make the sponge in the gas tank last for many years is to constantly clean the gas tank from rust and debris.

But here is the thing, as much as the process to clean up a gas tank is easy which could take less than 15 minutes – from making sure that every inflammable object is safety tuck away to draining the tank of gas and of course to putting them back could be done in less than 15 minutes. Especially if you’re someone with little or no basic experience. 

This is to show how easy it is to clean the gas tank.

However, you need to be very careful when cleaning your gas tank to avoid destroying your engine.

Here is a warning:

While changing the gas tank may sound like a good idea, it can potentially harm your engine”

Keeping a lawnmower out of use for a long time can make it difficult to fire up the engine the next time the lawn needs some care. This is the same with other outdoor garden tools from blowers to mowers.

To keep these basic pieces of equipment from breaking down three basic elements need to run smoothly:

  • Air
  • Spark
  • Gas

If you take time to clean your air filter correctly, the filter will always have clean air and when the mower plug is properly cleaned, it will stop it from sparking. However, if you fail to channel the gas properly at the right time and right amount, it might affect the performance of the equipment. Sometimes it makes the device not to run at all.

Why The Lawn Mower Carburetor Could Get Damage When CleaningThe Gas Tank

Draining your gas tank almost very often socould potentially harm your mower. The carburetor is the engine room of the mower. It is the ‘heart’ which stands as the most important organ of the engine. Its major role is to blend the air and the gas and make sure they circulated properly into the engine cylinder.

So every time you drain the gas tank, you are unknowingly adding more pressure to the most critical ‘organ’ in your machine.

When you drain gas off your tank, you allow air to enter the lawn mower’s carburetor.

Besides, it’s almost an impossible task to make sure you drain the last drop of the gasoline out of the tank. 

When air filters get mixed up with small gas droplets left behind, it causes gum and if these gums settle where it shouldn’t – like settling in the needle valve tip, then the carburetor will need a complete cleaning to restore it to working condition.

Allowing your lawnmower to sit empty for a long period gives room for water vapor to condense. 

And this condensed vapor can trigger corrosion in the tank, the carb, and cylinder and can make the engine fail.

However, if you properly clean the gas tank and leave the sponge in the gas tank as it is, you will have a mower that works at optimum performance and can be reused year after year.