any advice re stale diesel

[neilrob]

Hi There
I need advice
I am buying a steel motorsailer in Australia. Just came thru survey well. My problem.
The boat was winterised in 2002, the diesel tank was filled and treated with additives at that time. Now motor dewinterised his week (volvo dealer used fresh fuel). So the diesel (1800 ltrs) has been the tank for six years. What should I do to determine if the diesel is ok or how much risk am I taking a risk of doing engine damage? I have been told hat if i use additional filters it will be ok.
I posted this thead previously in monohulls by mistake
thanks for any advice Neil

[Pblais]

The age alone is not the real issue. The fuel may be fine but what else is in the tank may be of more concern. Moisture that accumulates leads to other problems and more solids in the fuel tank that can cause you problems with your filters clogging up easily and often. You have enough fuel that it is worth some testing and perhaps a polishing service. That would cycle the the fuel through a large set of filters and you would see the condition of the fuel and the tank. Even if you just pumped out the fuel you still have what else is in the tank.

[Ex-Calif]

If you are buying a boat that can hold 1800 liters of fuel I am guessing it is a big boat and cost a fair few boat dollars.

As sad as it may sound, I would dump the fuel (sell for heating oil?) change all the filters and put new fuel in. Risking your investment on 6 year old fuel is bad karma in my humble opinion.

My 2 cents worth will cost you a bit more. If you disregard my expensive advice I will surely understand.

[S/V Antares]

At the very least you should have the fuel Polished by someone that has the proper equipment. Not just an old racor like so many have. but a centrifical separator like an Alfa Laval. I recently got an old diesel running after 7 years but the old fuel would not kick it off. Had to run it on new fuel. The owner later mixed in 25% Jet A and said it ran fine but I was not there. Good luck!

[Trekka]

On the subject of storing diesel fuel... I have a 70gal tank on my boat but use only several gallons a year (so far). What additives are actually useful and effective for keeping the fuel as clean and viable as possible? There are several additives available, and all make great claims for what they do. But does anyone actually know which are useful and effective?

[Alan Wheeler]

Alfloc make a "real" additive. No silly claims. It just does as it is supposed to do. It has a biocide that will keep growth at bay. If the tank is full and sealed so no moisture can get in, the fuel will last a long time. Air access will also mean the tank has water access. Simple rule of fuel is, No water= No growth!.
There are fuel stablizer products available. IMO they are not stabiliziers at all. Just Centane boosters. Not something I would worry about. However if you are ion colder climats than I am used to, winter additives are essential to stop fuel from waxing and seperating out due to cold.

[neilrob]

I have now had a sample of the diesel tested and at an intertek lab. The results were a lot of numbers.The comment on the test certificate was that the diesel is surprisingly good for the its age. of course I took this sample from the top of the tank and so it offers no clues as to the condition of the bottom re sediment and water contamination
Thanks for the advice re cleaning and polishing as i have now bought the Boat Neil

[SkiprJohn]

Aloha Neilrob,
Welcome to the forum of many opinions. I would pump out the old diesel, decant it and filter it back into your tanks once you have cleaned them.
You are right to suspect anything deep in your tank. That's where all the crud settles. If the boat does a lot of moving around in a seaway all that stuff can start to be sucked up into your fuel lines. A good fuel polishing outfit can save you a lot of work.
Good luck,
Kind regards,
JohnL

[delmarrey]

I'll ad my peso.

I would agree about the fuel polishing. But if it were mine I'd pump out all the fuel and do an inspection of the bottom of the tank(s).

And depending on the material of the tanks is how I'd follow up. If they are steel and the tanks looks black on the bottom, I'd be concerned. If water had been sitting in there a long time it could have developed some erosion causing pin holes.
Aluminum tanks would have the same problem but it would take much longer to eat thru.
Plastic tanks would most likely be OK but being 1800 ltr (480 gl.) I'd think they would be metal.

All fuel tanks have a vent line which can draw in moisture. If the boat were stored in a hot dry climate the chances of moisture is slim............_/)