Diesel Fuel Fungus

Diesel Fuel Fungus Contamination

Are you fed up with the dirty slime build-up caused by diesel fuel fungus in your storage tank? Well, I know how vital fuel tanks and storage systems are in maintaining the regular efficacy of agricultural, marine, or fleet activities. 

But unless you ensure the diesel is not contaminated and take proper preventive measures, you cannot expect your system to run at its full efficiency. For diesel-operated vehicles or machinery, using high-grade fuel along with proper maintenance is crucial.

The untreated tank or storage system can act as the thriving place for microorganisms like fungus resulting in microbial contamination that degrades the diesel quality and can cause havoc in the engine!

Microbial Growth

Today’s environment-friendly diesel is a mixture of 7% biodiesel and 93% petroleum diesel. Well, this blend may act as a milestone to save mother-nature from carbon dioxide contamination but essentially not be favourable to the businesses that need to stock the fuel. 

Microbes like fungi and bacteria are the main culprits to cause microbial growth in diesel. The process gets accelerated when these microbes get an optimal condition inside the storage tank, that is, 10-40 degree temperature and the presence of water.

Biodiesel, being hygroscopic, attracts and absorbs water from the atmosphere more than gasoline or other types of fuels that help attain the optimal state. 

But how can these fungus spores get into the storage tank? Let’s get insight into the ways:

  • The microbes like fungus and bacteria are the natural inhabitants of soil and thus remain in the fuel to a specific degree
  • They can also get into the storage tank carried by air through the air vent
  • Any contamination during the filling process can lead to microbial growth 
  • When the hot fuel produced by the diesel engine goes back to the injector, it creates water from condensation. This water vapor condensation inside the fuel tank spurs the microbial growth by producing the optimal condition inside
  • Microbial growth usually takes place at the interface of the diesel and water close to the bottom part

This microbial growth appears as dark slime commonly compared to ‘chocolate moose’ sometimes. It looks like algae, and when the diesel remains unattended, and the condition deteriorates, it results in sludge accumulation. 

Signs of Diesel Fuel Fungus Contamination

Are you suspecting your diesel fuel is getting contaminated by microbes? Look for the following characteristics to come to a decision:

  • As contaminated fuel cannot generate power like a clean one, there may be an increase in the fuel consumption rate
  • You may need to replace the fuel filters frequently due to the clogging the microbes byproducts create
  • The fuel injectors may need frequent replacement or cleaning.
  • A change in color from bright yellow-green to dark khaki
  • The diesel may smell like a ‘rotten egg’ because of the sulfuric acid byproducts inside the tank
  • Wearing of cylinder lining and piston rings because of the acid corrosion caused by the contaminated diesel
  • Instead of clean exhaust, you may notice black exhaust smoke when the system starts 

If you notice any or all of the above signs, chances are, your fuel storage system is infested with microbial contamination!

Problems Caused by Microbial Contamination 

Microbial contamination can lead to severe harms to the engine and fuel tank, leading to:

  • Injector dysfunctioning
  • Fuel flow issues
  • A decrease in combustion efficiency
  • Plugged filters
  • Increase corrosion
  • Engine failure!

Preventive Measures

The best way to fight off microbial contamination in the fuel tank is to prevent it. The preventive steps are:

Fuel Monitoring

Fuel monitoring involves ensuring routine testing to detect the microbial growth and taking steps to minimize the issues it can create. For fuel monitoring, you should always rely on a test kit like Fuelstat Conidia Bioscience that is designed based on immunoassay antibody technology to give accurate results within 10-15 minutes!

Fuel System Maintenance

To prevent microbes from growing in the fuel tank, you need to limit the exposure of diesel to water. You can recycle the diesel by water separation, discharge the water from the bottom of the tank, or adopt the fuel tank insulation process for keeping the temperature stable. 

Fuel Treatment

If you notice microbial growth inside, you need to remove the sludge build-up and treat the bottom of the tank to stop further contamination. Using authorized diesel fuel biocides can be a great help in eliminating and preventing the sludge.

While using a microbial growth remover, make sure it is compatible with fuel, additives, or system components. 

Other preventive measures you can adopt:

  • Buying fuel from trusted sources
  • Keeping the tank clean, leak-free besides periodic monitoring
  • Following the recommended methods of fuel refilling
  • Keeping diesel cool and away from copper, zinc, and metal alloy
  • Ensuring filtering the fuel when it is moved
  • Keeping the tank full to minimise water condensation. 


Diesel fuel fungus has become the prime cause of engine failure nowadays. Thus there is no alternative to testing, monitoring, and using chemical biocides to combat the contamination and keep the diesel in its best condition!

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