How to identify and prevent Diesel Bug and Fuel Contamination 

Diesel bug and fuel contamination can be difficult to avoid and can damage equipment and machinery. In this guide, we explore what fuel contamination is, how it happens, and how to ensure it doesn’t affect your operations.

What is fuel contamination?

Contamination occurs when an unwanted substance is present in the fuel. If it goes undetected and the fuel is used in machinery, it can cause significant issues, damage equipment, and, in the worst-case scenario, shutdowns. Depending on the cause of the contamination, the fuel may be treatable or need to be disposed of.

What is diesel bug?

Diesel bug is a term for microorganisms that grow when diesel comes into contact with water. Affected fuel can cause engine damage, corrosion, black smoke, difficulty starting machinery and increased fuel consumption.

What does diesel bug look like?

When diesel bug develops, it appears as a slimy, sludgy deposit that can range in colour from dark brown to black and often has a distinctive rotten-egg smell.

What causes fuel contamination

Contamination can be caused by several different things, including:

• Water: Fuel can become contaminated with water due to leaks, humid air entering the tank, and water vapour condensing inside the tank.
• Microbial growth: Microorganisms like yeast, fungi, and other bacteria are always present in the air and can contaminate fuel anytime. This type of contamination is also known as diesel bug.
• Particulates: Rust, dust, or other contaminants from other equipment and machinery can enter the fuel tank when it’s open or if the contaminants are airborne.
• Asphaltenes: Asphaltenes are a black, tar-like substance that forms in diesel fuel when it ages, when it’s heated or pressurised, or if it becomes contaminated by other substances.

Contamination can cause significant damage to machinery and equipment, resulting in downtime and repair costs, especially if it affects an entire fleet.

Fuel contamination symptoms

Contamination is usually only noticed when machinery and vehicles are affected. Still, if you know what to look for, it can be caught before it’s used and causes any damage.

• Does the fuel look different? Is it cloudy or dark?
• Does it smell different? Contaminated fuel can smell bad or like varnish.
• Do you see any floating debris or sludge in the tank? This could indicate contamination.
• Is the tank damaged or showing signs of wear and rust? This could compromise the fuel inside.
• Could water have entered the tank? Rain could have got inside the tank, a common cause of contamination. For insights into how to weatherproof your fuel storage solutions at events, read our full guide here.

If you think contaminated fuel has been used, look out for these signs in machinery and equipment:

• Filters frequently become clogged or need replacement.
• Experiencing more smoke than usual from the exhaust
• Reduced engine performance
• Difficulty accelerating
• Check engine light may come on

If you notice any of these things, your fuel is likely contaminated, and you should stop using it immediately.

Fuel contamination testing

While contamination can often be spotted by looking out for the signs above, sometimes you’ll need to test your fuel to identify if your fuel is contaminated. The process varies according to the type of contamination:

• Particulates and asphaltenes – If these are too small to identify visually, they can be identified by chemical analysis.
• Water-testing kits are widely available to identify whether the water level in your fuel is above or below 30 parts per million.
• Microbial contamination – Microbial contamination is more challenging to identify. Tests for this kind of contamination, also known as diesel bug, usually require a fuel sample to be sent to a lab for analysis.

How to prevent fuel contamination

Fuel contamination is much easier to prevent than fix, so you should take steps to eliminate the chance of your fuel being contaminated. There are some processes that can help with this.

Inspections

Visual inspections can help catch contamination once it has begun, but it’s better to identify signs of contamination early to avoid the risk of your entire fuel supply becoming unusable. We’ve already looked at the visual signs above, but look out for:

• Dark or hazy fuel
• Any evidence of rust inside the tank
• Floating debris
• Scum on the sides of the tank

Monitor and clean your tank

Keeping your tank in good condition is crucial in limiting the chances of contamination. Here’s what you should do:

• Look out for any rust on the outside or inside of the tank.
• Inspect seals, hinges and joints. If plastic or rubber seals perish or fail, it’s much more likely that water or other substances will get into the fuel.
• Clear away any pooling water on the top of the tank as soon as possible. In colder weather, the freeze-thaw effect can cause damage to the tank.
• As part of maintaining your tank, you should have it professionally cleaned. This is because sludge and other substances can be hidden at the bottom of your tank and may not be noticed on visual inspection. If your fuel level runs low, this sludge can be pumped out and into machinery, causing serious issues.

What to do if you have contaminated fuel

What you need to do depends on the severity of the contamination.

If you have excess water or diesel bug in your fuel, you can try to salvage the fuel by using an additive or by fuel polishing (filtering the fuel to remove water, sediment and microbes).

If the fuel isn’t salvageable and the contamination is severe, you should drain the tank and fuel lines and clean the tank to remove any sludge or sediment. When you refill the system, flush it out with fresh fuel.

How to treat diesel bug

The most effective way to treat diesel bug is usually fuel polishing. This allows you to retain the affected fuel. A fuel additive containing a biocide that targets and kills the diesel bug is also sometimes suitable for use. When treating diesel bug, you should always thoroughly clean your tank, filters and lines to avoid recontamination.

Avoid fuel contamination with a Western Global tank

As we’ve discussed, contamination can be costly and time-consuming. It’s better to avoid the risk of contamination altogether, and with a Western Global tank, your fuel has the best chance of remaining secure and uncontaminated. Our popular TransCube Global has a number of features that help to limit contamination, including:

• Removable inner tank – A removable inner tank makes inspection, cleaning and maintenance straightforward. Allowing you to stay on top of your fuel supply more easily than other tanks.
• Manway access – Gives you access to the inner tank, making inspecting fuel and performing maintenance straightforward.
• Secure equipment cabinet – Ensures fuel, ports and other equipment are kept safe and reduces the opportunity for contaminants to enter your fuel.
• Strong, rust and corrosion-resistant galvanised steel frame – The durable structure of the tank ensures that contaminants won’t be able to enter through weak spots or cracks.
• 110% bunded containment – The in-built bunded containment eliminates the need for drip trays. Secondary containment that’s left out in the elements may collect water where microbial contamination may be more likely.

Browse our range of tanks to find the perfect solution for your fuel storage needs.