What causes the discoloration/contamination of diesel on boats.
I filled my tank a few years ago with contaminated diesel from various places around the world.
I emptied my diesel tank two years ago, and refilled with clean diesel. I changed the filters a year ago, and the diesel was still clean. I thought the problem had gone away Recently my engine failed leaving harbour in 20 knots of wind, so I sailed back into the harbour. On rectifying the problem, I noticed that once again my diesel is black/contaminated.
Does anyone know what is causing the diesel to become contaminated? Age/Water/condensation/bacteria perhaps. How can I stop this happening?
My diesel tank when full holds 34 gallons enough to run for 72 hours. I do not use this amount of diesel in 2 years under normal conditions. Would I be better off just maintaining approx 5 gallons in the tank? or does running with an empty tank allow for more condensation inside the tank, and more water contamination.?
Looks like the Wiki article you found is quite informative and there isn’t much more I can add to that.
I will just say that what you describe is almost certainly some sort of microbe infection. I use the word infection very deliberately here, rather than contamination, because it is an important distinction that needs to be made, both in thinking about the problem and solving it.
The microbes need only a small amount of water to live in and the diesel fuel is the food that they feed on.
The dark slimy stuff that clogs fuel filters and injectors is their waste products. You can clean filters and injectors, and replace the fuel over and over and the infection just keeps coming back, again and again.
The only way to deal with this is by using an antibiotic, actually a biocide that kills the microbes on contact. I won’t recommend any particular brand names, there are several on the market; just be sure it is a true biocide and not some preventative agent. Don’t worry about the danger to marine life because it stays in your fuel tank and is completely combusted along with the fuel.