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What Happens If You Fill Your Gas Tank With Water?

what happens if i fill my fuel tank with water?

What Happens If You Fill Your Gas Tank With Water?

Have you ever wondered what will happen if you fill your gas tank with water and then try to drive your vehicle? Well, at least some of us might have. Water is often used as a coolant in car engines, and it’s also used in the radiator. But, using water as the only coolant isn’t a good idea.

The main issue with water in the gas tank is that water doesn’t compress like gasoline. So, when you try to start the engine, the piston will come up and hit the water, causing a Hydro-Lock. This will cause serious damage to your engine, and it might even ruin it. Not only that, but the water can also seep into fuel storage tanks and contaminate the gasoline. This will make your car run less efficiently and can cause damage to the engine over time.

So, what happens if you accidentally put water in your gas tank? Let’s discuss it in detail.

What Happens If You Put Water In A Gas Tank?

filling car with fuel
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Modern vehicles have a fuel door release button; it’s unlikely that someone will pour water into your gasoline tank as an act of mindless mischief. However, if you are driving an older vehicle with a gravity-fed fuel tank, accidental water contamination becomes much greater.

When you put water in the gas tank, it will mix with the gasoline and be drawn into the engine. As the water is being pulled into the engine, it will compress and can cause serious damage to the pistons and other internal components.

In addition to causing mechanical damage, water can also contaminate your gasoline supply. This can lead to several issues with your car, including decreased fuel efficiency, reduced performance, and even engine failure over time.

At the same time, the water and gas combo can also cause rough stalling, sputtering, and starting problems. Furthermore, the contamination can eventually clog fuel injectors and carburetors.

These problems can be expensive to fix and may even require you to replace your engine. So, it’s important to be careful when filling up your gas tank and always check the nozzle to ensure that water hasn’t gotten into your tank by accident.

Symptoms Of Water In Gas Tank

inside an engine
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If you suspect that you have put water in your gas tank, there are a few signs that you can look for. Some of the most common symptoms include:

1- Check Engine Light Illuminate After Refueling

Your car engine mostly looks for the issues like – wrong air to fuel mixture, low compression, and ignition timing. All these can easily trigger the check engine light. So, if your engine reads the misfiring from water-contaminated gasoline, it will turn on the check engine light.

2- Sputtering and Stalling

If you are driving and suddenly your car starts to sputter, it is one of the first signs of something wrong with the gasoline. The water in the gas will cause the engine to run lean, leading to stalling and sputtering.

3- Reduced Fuel Efficiency

If you notice that your car’s fuel efficiency has decreased, it could be because the water in the gas is causing the engine to run less efficiently.

4- Vehicle Stalling Right After Refueling

The gasoline engine can’t run on water, so if you have just put water in your gas tank and tried to start it, it will stall immediately.

5-Reduced Fuel Efficiency

Another common symptom of water in the gas tank is decreased fuel efficiency. This can mean that you may have to fill up more frequently or that your car simply isn’t running as smoothly as it should be.

How To Check If There Is Water In The Gas Tank?

the engine bay
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There are a few different ways to check for water in your gas tank. One of the simplest methods is to look at the color of your gasoline. If the gas is darker than usual, it may be because water has contaminated the supply.

Gasoline weight is almost 6 lbs/gallon; at the same time, water weight is 8.3 lbs/gallon. So, you can check the weight of your gas tank before and after refueling to see if there has been any significant change. Also, the water separates from gasoline, so if you see water droplets in your gas tank, it’s a sure sign that there is water contamination.

Another way to check for water in your gas tank is to use commercial test kits to test for moisture. You can also take a fuel sample and put it on a clear plastic sheet. If there is water in the sample, it will bead up on the surface of the plastic.

How To Remove Water From The Gas Tank?

open bonnet on car
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If there is a small amount of water in your gasoline task, you don’t have to worry, as all petroleum contains a small amount of water. For example, E10 fuel contains almost 0.5% of water.

However, a significant amount of water can be problematic. The best thing is to drain the tank and refill it with fresh gasoline. However, if you can’t drain the tank, you’ll have to remove the gas yourself.

One way to do this is to use a commercial fuel dryer designed to absorb water from the gas. You can also try using an old coffee filter to remove any water from the gasoline.

If you’re still having trouble removing water from your gas tank, it’s best to take your car to a mechanic or service station and have them drain the tank for you.


guy filling up car with fuel
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The best way to avoid putting water in your gas tank is to be careful when refueling. Always make sure the nozzle is properly inserted into the tank, and be careful not to spill any gasoline on the ground. 

If you notice your car sputtering or stalling, it’s important to get the problem checked out. And finally, using a fuel dryer can help prevent moisture buildup in your tank, which can reduce the risk of water contamination.

The Bottom Line

Water and gas mixture in your gas tank can wreak havoc on your car, so it’s important to be careful when refueling. Filling up your tank with contaminated fuel can cause several issues.

If you think there may be water in your gas tank, it’s best to get the problem checked out by a mechanic or service station.

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