Gosh I am very rusty on all this now. But tell me, as it is fuel for a boat, is this ordinary road diesel, or is it MDF, i.e. marine diesel fuel? I think that sometimes MDF can be a blend including some heavier components, which can include aromatic species called asphaltenes that may become unstable over time and precipitate out. But if it is just road -type diesel fuel then the explanation must lie elsewhere.
I found this link: https://offers.bellp...5-ea2d6cf1b988
which suggests that the ultra-low sulphur road diesel fuel used today has poorer oxidation stability (which certainly makes sense from what I remember from my years in the lubricants industry with Shell) and can be more prone to bacterial growth. These guys are in the business of selling chemicals to inhibit this sort of thing, so they may be talking it up but it does not look like snake oil to me.
Over the last few years I have filled my tank from various sources, from outside of Europe. Marine diesel was banned a few years back in Europe in pleasure boats and also I think commercial fishing boats. I have filled everywhere from UK through southern Europe Carribean Panama Ecuador Peru Many Pacific islands New aealand Austrailia, Indonesia Malaysia Thailand Mauritius South Africa Brazil Caribean Atlantic Islands. Some of the fuel has been so bad in Indonesia that it was filtered before putting into tanks through nylon stockings. Fuel filter replacements were very regular. Diesel in Brazil may have been bio diesel, from sugar cane.
I tried pumping the tank empty 2 years ago and refilling with clean European diesel, which is the same as is used in cars, and is no longer subsidized.
I am torn two ways > water build up in diesel is due to condensation inside the tank, not break down of the diesel, so would it be better to keep the tank full to prevent humid air entering the tank?
since fuel degrades and I use little fuel ie a full tank of fuel can last two years now. Would I be better off just putting a small amount in my tank rather than refilling to ensure I have fresh fuel?
Diesel floats on water, "normally". If it sits inside a stationary fuel tank. Is the bacterial growth in the water at the bottom of the tank or is it in the diesel. I have a tap at the bottom of my fuel tank that could be used to drain water theoretically, but when it is opened only diesel comes out suggesting that perhaps the water is well mixed with the diesel, assuming that water is the cause of the bacterial muck in my diesel.
Last week I placed a chemical into my tank to fix bacterial problems, it is very toxic to marine life, and apparently very poisonous, I have not examined the diesel since I gave this treatment but assume it is still discolored. Since then I have managed to concern my self with another question, my diesel tank is fibre glass, and I have rubber seals around the fuel line joints. Can additives to treat diesel damage fibre glass or rubber joints, I note the chemical was contained in a plastic bottle, which eases my mind somewhat, BUT I recall some one speaking about chemicals eating his fibre glass fuel tank a few years back. I suspect my fuel tank is made of Polyester resin and not Epoxy resin. Would this make a difference.
Edit I thought I would do a quick wiki search this link appears to cover most of my dirty diesel questions https://en.wikipedia..._of_diesel_fuel. I dont think I will fill my tank again unless I am going long distance, or somewhere there is no wind.
Edited by Flummoxed, 02 November 2019 - 04:37 AM.