Cloudy Diesel Fuel: What It Means and How to Fix It to Keep Your Engine Running Smoothly

Wed, Dec 2, 2020

Whether its road diesel or red diesel, your fuel should appear clear and bright. Regardless of it being yellow or red, you should be able to see through it similarly to water. Cloudy is not what you want to see.

If you have taken a sample of your fuel and wondering why is my diesel cloudy, or maybe worse, it’s lost all transparency and it is now a milky consistency, then you have a problem with water contamination. This article will explain what the cause of cloudy and milky diesel fuel is and how you can fix it, as well as prevent it from happening again in the future.

Types of water contamination in fuel

So, what causes diesel fuel to look cloudy?

What is obvious is that cloudy fuel is not what you should see and it indicates a problem with water contamination. But, to really understand why you have milky fuel or what makes diesel fuel cloudy, it is important to understand the difference between free water, suspended water or emulsified fuel.

As you probably know, fuel can become contaminated with water through rainwater, condensation and also due to the natural water content in today’s biodiesel. What you may not know, is that water contamination within diesel fuel can occur in three ways; free versus suspended and emulsified water. So what is the difference and why does this mean for cloudy diesel fuel?

  • Free water – As its name suggests, free water is present within the tank but exists completely separate to the fuel. It sinks to the bottom of the tank, creating a layer of water under the fuel. It is here that diesel bug often grows which puts your equipment, vehicles and engines at risk.
  • Suspended water – Now, it is this type of water contamination that is responsible for your cloudy diesel fuel. Suspended water is that which is bound to the fuel molecules and is essentially mixed in with the fuel making it appear cloudy. As the diesel becomes so full of water that it can hold no more it starts dropping free water out to the bottom of the tank.
  • Emulsified fuel - Under pressure changes, agitation and heavy cavitation, often experienced as the fuel passes through pumps and filters, the water content can become completely emulsified turning it from cloudy to milky diesel fuel. This is where there is almost no separation between the fuel molecules and water content.

If you have taken and found a cloudy diesel fuel sample, we recommend that you also take a sample from the bottom of the tank as it is likely that you also have a problem with free water. It is vital that you act on both types of water contamination immediately as it can have devastating impacts including diesel bug/nasty sludge growth, blocked filters, damaged pumps, engine failure and fuel system corrosion.

Fuel tank filter

How to fix cloudy diesel fuel?

If you have detected milky or cloudy diesel fuel then you need to act to avoid costly repairs and equipment downtime. But how do you do this?

1. Fuel tank filters

Standard fuel tank filters designed to remove the water before it is dispensed into your vehicle or equipment are a great solution for eliminating the free water, but unfortunately, they do not get rid of emulsified water. Whilst they are a cost-effective solution to deal with the one side of fuel contamination, they are unable to remove the water that is making your diesel appear cloudy. In addition, standard fuel tank filters only deal with the problem once the fuel is being dispensed. As they do not aim to remove the water content whilst it is sitting store in the tank, they do not solve the problems associated with diesel bug growth and sludge formation.

2. Fuel polishing

Fuel polishing is a solution that will fix cloudy diesel fuel. This service is usually undertaken periodically by a professional and involves removing the fuel from the tank and passing it through highly efficient filters that remove contamination down to the EN590 quality standards of diesel fuel. After fuel polishing has been carried out, both the free and emulsified water content will be removed down to the required 200ppm. But what happens to the water content in your tank between fuel polishing services?

Before and after

3. Aquafighter fuel tank water absorber

Whilst there are other diesel tank water absorbers on the market, Aquafighter is the only fuel tank water absorber on the market that also successfully removes the suspended and emulsified water that causes the cloudy and milky fuel.

The beauty of this solution is that all you need to do is simply place Aquafighter in the tank through the largest opening of a storage tank, genset belly tank or vehicle fuel tank, and the diesel tank water absorber reduces water content levels down to less than 75ppm. Therefore meeting and exceeding the EN590 diesel fuel standards of 200ppm. By working in this way, Aquafighter fuel tank water absorber keeps your fuel tank free of water and cloudy fuel at all times, without the effort of removing the fuel from the tank first.

Now you know what milky or cloudy diesel fuel means, you will know why it is so important and how to act on this side effect of water contamination before it causes a serious issue.

For more fuel contamination helpful advice, handy tips and prevention solutions follow our #FuelContaminationFriday series on LinkedIn and Twitter.

Searching for solution for cloudy diesel fuel?

View our Aquafighter water absorber range; a complete solution to removing free and emulsified water that causes cloudy diesel fuel.