West Marine Services
6 Marine Trade Centre, Brighton Marina, BN2 5UG
01273 626656 / 07824 641888
Mon-Fri: 08:00 - 16:30

What is diesel bug?

Diesel bug is a generic name for the microbial contamination that grows in diesel fuel.

What are the different types of diesel bug?

The diesel bug is not a single type of organism. There are thousands of different types of bacteria, mould and yeast found inhabiting fuel systems. This kind of contamination is hard to predict as every system offers a unique environment.

There are broadly four categories of diesel bug:

  • Bacteria: single cell organisms, typically 0.3 to 60µm in size. A colony can double in size in 20-30 minutes. One cell can multiply into 2 million in 7 hours. Bacteria will degrade quality fuel over time.
  • Mould: a type of fungi with long multi-cellular filaments. There is little indication that mould degrades fuel but, due to the long strands, it does block filters.
  • Yeast: another type of relatively slow-growing fungi. It is typically 3-4µm in size.
  • Biofilm: a complex structure of microbes which adhere to the walls of the fuel tank and to each other. It begins to form when free floating microbes land on a surface and attach themselves to it. Given time, biofilms can grow many millimetres thick and produce a protective slime. Biofilms can excrete acid which can erode a metal fuel tank. Chunks of biofilm can slough off periodically, giving microbes the opportunity to infect other areas of the fuel system and block filters.

How can you stop diesel bug growing?

Prevention is always best. The key to maintaining fuel quality is good housekeeping. West Marine Services recommends following a comprehensive fuel conditioning programme to ensure that your diesel-powered equipment runs reliably and economically. Effective programmes include four stages: testing, cleaning, polishing and stabilisation.

  • Testing: take samples of fuel at regular intervals, either use The Marine 16 Diesel bug testing kit or we can send the fuel to Volvo Penta’s chemical lab for more detailed results with advice moving forward
  • Cleaning: the physical cleaning of your tanks, filters and metering equipment, this can be done by a number of means but the end result guarantees clean fuel from the offset
  • Polishing: this is done using machinery, the fuel is pump from your tank around a centrifugal filtration system at high pressure, the fuel is then returned to you tank, ideally at the opposite end form the collection point, this creates movement within the tank which can assist in removal of the Fuel bug from the tank walls.
  • Stabilisation: chemical treatment, it is imperative that every time you refuel that a Marine 16 fuel conditioner is added, this not only prevents the regrowth of the fuel bug but can also can improve fuel efficiency and performance.

Technical Tips

If you have a badly contaminated fuel tank you should be able to treat it and not clean it out. Use a shock dose (100ml to 100 litres of fuel) of Marine 16 Diesel Bug Treatment, stirring in if possible. Leave for 72 hours and then add Marine 16 Diesel Fuel Complete at 500ml to 375 litres. The Diesel Fuel Complete will increase the cetane rating of the fuel and clean your injectors and fuel lines. This should enable the engine to run normally without worry. The sludge build-up in the tank may take a couple of doses of Diesel Bug Treatment to fully break up and disperse but it is a lot cheaper and easier than removing and cleaning a tank.

Remember that if you do opt for tank cleaning one remaining organism in the system can kick off contamination again so use a regular (100ml to 2000 litres) dose of Diesel Bug Treatment to ensure you never have the problem again.

Marine 16 Diesel Bug Treatment is currently on Special Offer at our shop with 10% off. 

Call us on 01273 626656 or pop in to see us at Brighton Marina, opposite the boatyard.