Diesel Bug Information

There are known to be over 20 species of fuel bugs that can take-up residence in your fuel tank and they aren't fussy whose tank they treat as home - they don't care if you own a super yacht, motorboat or narrow boat. If the conditions are suitable they 'move in' and start to multiply. Without making an appointment to view a potential new home, the fungal spores are carried by air and water, entering your fuel system via filling ports and vents. The air space above the fuel in tanks contains water vapour. The walls of the tanks are cool and the water vapour condenses on these surfaces. This water subsequently accumulates and sinks to the bottom of the tank creating an ideal environment for the growth of the most common of fungi "Cladisporium resinae".


Once in a fuel supply these unwelcome guests exist virtually undetected and wait for the right conditions for growth. They can double their numbers every 20 minutes and one single spore can produce over 260,000 cloned descendants in six hours. Each spore lives for about 48 hours and as older fungi die their bodies accumulate, forming a slime that ultimately floats upwards into the fuel - so it doesn't take long for the bugs to dominate the entire fuel system.

Fungal infestation can 'spoil' the fuel and as the sludge is drawn into the engine, quickly clogging filters, causing loss of power, narrowing fuel lines and eventually leading to engine breakdown. No fun if your engine stops when battling against a force 8 gale and strong currents! The damage does not stop there. A portion of sludge adheres to the inner walls of the tank and fuel lines producing corrosive hydrogen sulphide that causes metal defects and pitting of the injectors and fuel related components.

Condensation will occur at the refinery, fuel depots and fuel jetties, in holding tanks and in all boat tanks. At the fuel/water interface there is both hydrocarbons and dissolved oxygen providing the idea environment for the dreaded bug.

Cladisporium resinae can have many guises ranging from mousse, treacle, candyfloss, cotton wool etc and forms tangled threads a few microns in diameter, forming thick, tough mycelium mats at fuel/water interface. These micro-organisms will consume rubber gaskets, O-rings, hoses, tank linings and coatings in an effort to obtain their mineral content.