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Diluting gasoline with water has been a common accusation that people think gas stations perform. And recently, a startup has developed a process where diesel fuel droplets are infused with nanometer-sized water particles. It is said to lower diesel fuel costs and also significantly reduce carbon emissions. But can you actually use water to dilute gasoline? Let’s look.

Do gasoline and water mix well?

Water and gas
Mixing water and gas | Getty

To mix the two liquids they need to be of the same density or weight. Otherwise, the heavier of the two will settle to the bottom of the container or tank. Water is about a quarter denser than gasoline, so the heavier water won’t mix but, instead, sinks. 

So that means that mixing can’t occur. The gas floats to the top, leaving the heavier water at the bottom of the fuel tank. So no, you can’t dilute gas with water. 

Gasoline in modern fuel-injected vehicles is picked up by the fuel pump from the top. So initially, the vehicle will run smoothly. But as the gas is used and the pump starts to pick up the water, the engine will die. And without the ability to ignite water, it can’t be started. 

Water doesn’t burn like gasoline, but it can freeze

filling jerrycan
People fill a jerrycan at a gas station | Getty

Another problem with water in the fuel tank is that in freezing conditions, it may harden at the bottom of your tank. You’ll end up with a big block of ice. If the water does make it into the fuel system, it can also clog fuel lines. Fuel delivery is blocked, which can lead to burning out the pump or at least result in shutting the engine down. 

A small amount of water can seep into the tank for various reasons. If the happens you probably won’t even be aware of it. Filling up without a canopy to protect from the rain is one way this can happen. 

Can it be dangerous?

Gas going in
Gas nozzle being put into a gas tank | Getty

But in the case of trying to mix it into gasoline, it could be catastrophic. At the very least, the tank and fuel system will need to be purged before refilling the tank with 100 percent gasoline. So the best thing you can do is avoid getting any water into the fuel system. 

Let’s say you do get an unavoidable amount of water in your car’s gas tank. What can you do to remove it? According to It-Still-Runs, there are commercially available dry-fuel additives. So that is one way. But the other is to use what is the most common ingredient in the additive, dry isopropanol alcohol. 

Adding ½ ounce of IPA per gallon of gas should work. Once the solution is put into the gas tank drive the vehicle around. With continued use, the alcohol should help burn away the water. 

Siphoning the fuel out of your tank is another solution. Try to find a clear container to view the contents. After sitting for a while, the water should separate from the fuel. Then, if there is no other contamination visible, you can reuse the fuel and then throw away the remaining water.


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