What Are Positive & Negative Effects Of Adding WD40 To The Gas Tank?


WD40 is an all-purpose spray that helps maintain mechanical parts. However, many automotive enthusiasts online and in real life preach the benefits of adding it to a car’s gas tank. Before you follow their advice, consider the positive and negative effects of doing so.

There are many claims that adding WD40 to your gas tank will displace water, remove buildups and contaminants, and improve combustion in diesel engines. However, critics point out that doing that will also leave behind a gummy residue, foul your spark plugs, and compromise the oxygen sensor and exhaust system overall.

This article will help you get to the truth of these claims. First, you’ll discover the alleged benefits of adding WD40 to your gas tank and then see the adverse outcomes of doing so.

What Are The Benefits Of Adding WD40 To A Gas Tank?

There is a lot of information going around about the benefits of adding WD40 to your gas tank. However, you must first understand that none of those benefits has been proven correct.

That’s right!

Neither the manufacturer nor any other authority has claimed that adding WD40 directly into your gas tank is a good idea or offers any sort of performance or maintenance advantages.

Instead, most of the claims come from automotive enthusiasts who swear by it. Those people have gone online to preach about how the multipurpose spray or fluid can help your fuel system and engine function better.

So, regardless of where the claims come from, let’s look at some of the supposed positive effects you can enjoy from adding WD40 to your fuel system.

Read: Car Gas Tank Leak Repair Cost

1. Water Displacement

WD40 is a penetrating oil famous worldwide for its water displacement qualities. In simple terms, that means wherever you apply WD40, the fluid will keep water away. That’s why people use it to maintain moving metal parts and prevent corrosion.

Automotive enthusiasts claim that the water displacement ability of WD40 also works inside a car’s gas tank. Adding WD40 to the tank is said to keep water away and protect the tank from rusting.

Of course, spraying the can directly into the filler could take a while. So, if you’re going to do this, buying a liquid container of WD40 and pouring it in would be much more practical. That way, you can also measure how much you pour much more precisely compared to using a spray.

Read: Why There’s Gas Leaking from the Bottom of Your Car

2. Eliminates Contaminant Buildups

WD40 is also said to help eliminate contaminants inside your fuel tank and system.

That claim likely comes from the fact that WD40 is a penetrating oil. So when applied to your car externally, you can use it to effectively remove gunk, dead bugs, and other buildups by spraying it directly on the affected surface.

The idea here is that the penetrating ability of WD40 also applies inside your gas tank, which can help you eliminate any long-term buildups that exist.

3. Cleans The Tank And Fuel System

Overall, adding WD40 to your gas tank supposedly cleans the tank (e.g. by removing contaminant buildups, as explained above) and diluting them so they can flow away.

Since the WD40 will flow along with your gas, it stands to reason that the cleaning benefits will reach throughout the entire fuel system.

Read: What Happens if You Put Diesel in a Gas Car?

4. Improved Combustion In Diesel Engines

Even in the diesel world, many enthusiasts report positive benefits from adding WD40 directly into their fuel tank. The WD40 is said to improve the combustion process in diesel engines, reducing problems like excessive vibrations, shuddering, and even loud noises.

While these and other benefits are shared by automotive enthusiasts online, you must remember that the manufacturer does not make any claims suggesting you should do the same. So, if you try adding WD40 to your engine, remember that you’re doing so at your own risk.

What Are The Dangers Of Adding WD40 To A Gas Tank?

The usefulness of adding WD40 to a gas tank is hotly debated in the automotive world. However, just as there are enthusiasts who say it offers many positive effects, there is also a vocal opposition that says it does more harm than good.

Here are some of the negative effects of adding WD40 to your gas tank:

1. Gummy Residue Or Oily Film After Evaporated

Firstly, WD40 is known for leaving a gummy residue or oily film on a surface after it evaporates. As a result, critics say that adding it to your fuel tank will also result in the same problem happening inside the tank’s surfaces.

So, while the WD40 might penetrate and remove other buildups inside your gas tank, it will also leave behind one of its own.

Read: What Are the Symptoms of Fuel Tank Vent Blockage?

2. Foul Spark Plugs

Anything you put into your gas tank will flow throughout the entire fuel system. That means it’ll also end up in the engine’s chambers and interact with your spark plugs.

Due to that, adding WD40 to your fuel tank can lead to your spark plugs becoming fouled. That’s because the fluid interferes with the combustion process and adds to the wear experienced by those individual plugs.

3. Oxygen Sensors

Always remember that the combustion process isn’t just about what goes into the engine, but it’s also about what comes out the other end.

On the outgoing side is one or more oxygen sensors that help regulate your car’s overall combustion process. So, if the air and fuel mixture is contaminated with WD40, some will come out on the other side and affect your oxygen sensors.

For instance, the oily film and residue mentioned earlier will end up on the oxygen sensors and affect their ability to function correctly.

When the oxygen sensors are compromised, they’ll feed your car’s computer incorrect data. That, in turn, will cause your vehicle to send an incorrect mixture of oil and fuel to the engine and cause it to perform poorly.

Read: Why Your Car Is Leaking Gas

4. Emission System

Unfortunately, the oxygen sensors aren’t the only thing affected by adding WD40 to your gas tank. Instead, some car enthusiasts report that the emission system overall will become affected.

Any part of the WD40 that doesn’t get burned up in the engine’s chambers will flow through the system, potentially getting caught and forming buildups along the way.

Besides that, some will end up in parts like the catalytic converter, undermining its ability to remove other harmful contaminants from the exhaust gasses.

Should You Add WD40 To A Gas Tank?

No, you should not add WD40 to a gas tank. Despite the reported benefits of doing so, the potential risks outweigh them significantly. 

As a general rule of thumb, you should only add fuel to your gas tank and nothing else, as it could affect your engine and the entire fuel system.

Final Thoughts

You’ll find plenty of ideas online and in person about things you can add to your gas tank to improve your car’s performance. The idea that adding WD40 to the fuel tank has lasted a long time and likely comes from how WD40 has a long list of applications elsewhere.

Some people claim that WD40 in a gas tank will remove water, contaminants, and even improve combustion in diesel engines. However, the same can also cause damage to your spark plugs and exhaust system as a whole.

While the claims have some truth to them, it’s always best to only put the correct fuel into your tank.

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