Diesel - Use By Date ?

[STATUE]

I purchased the yacht 2 years ago where it has since been stored in a barn.

I did see the engine run for 3 minutes before purchasing.

This boat hasn't floated for 4 years.

Full tank of diesel.

What to do ?

 

[Moodysailor]

If the engine hasn't been layed up or preserved, I'd be more concerned with that than the diesel.

But regards your question, personally I would dispose of it and fill with new. Alternatively, you could remove it, filter it and then mix 50/50 with new and run it.

E10 diesel (which that likely is) can form deposits, and there may also be other "undesirables" in the tank (condensate, bug, etc) which will benefit from removal.

 

[JumbleDuck]

I'd take a sample from the bottom of the tank and if it looked OK, use it.

 

[HissyFit]

It is advisable to fill diesel tanks on layup, to deprive the potential diesel bug of the air required to grow. Since the tank were filled, it may mitigate the dire consequences. If possible, I'd set up a system whereby the fuel could be run through filters before returning to the tank, thus 'polishing' it. It should save you a lot of expensive wasted diesel, and it is a good system to have in the event of dirty new fuel. Diluting with new, as already suggested, would never hurt, so long as you've got storage for the extra volume.

 

[garymalmgren]

How much fuel are we talking about?
50 litres. 100 litres, 300 litres.
It would make a difference to me.

 

[Moodysailor]

It is advisable to fill diesel tanks on layup, to deprive the potential diesel bug of the air required to grow. Since the tank were filled, it may mitigate the dire consequences. If possible, I'd set up a system whereby the fuel could be run through filters before returning to the tank, thus 'polishing' it. It should save you a lot of expensive wasted diesel, and it is a good system to have in the event of dirty new fuel. Diluting with new, as already suggested, would never hurt, so long as you've got storage for the extra volume.

This is true, but as you can never eliminate the air in the pipework and vent, after this amount of time i wouldn't chance it and at minimum filter the fuel.

My concern would be that any sediment of gum deposits (E10 diesel has a "shelf life" of 12months) could be on the tank surfaces and the risk is that these get disturbed when the vessel starts moving, causing issues during use. I've seen this on more occasions than I care to remember.

 

[HissyFit]

This is true, but as you can never eliminate the air in the pipework and vent, after this amount of time i wouldn't chance it and at minimum filter the fuel.

My concern would be that any sediment of gum deposits (E10 diesel has a "shelf life" of 12months) could be on the tank surfaces and the risk is that these get disturbed when the vessel starts moving, causing issues during use. I've seen this on more occasions than I care to remember.

Re-reading what I wrote, it seems like I'm saying that filtering is an option. No, I agree entirely that the fuel needs to be filtered.

 

[Moodysailor]

Re-reading what I wrote, it seems like I'm saying that filtering is an option. No, I agree entirely that the fuel needs to be filtered.

Yes, sorry that I was unclear. i was agreeing with you and trying to add more context. ?

 

[RichardS]

I'd take a sample from the bottom of the tank and if it looked OK, use it.

I would do that ..... but before using I would chuck in a dose of injector cleaner and a dose of biocide and then add fresh fuel as soon as I could get a few gallons in.

Richard

 

[madabouttheboat]

I had a car parked on my drive for nearly 20 years. The tank was full of diesel to the tune of about 80 litres. The fuel tank had a drain bolt and being a 4X4 plenty of room underneath. I drained it down and the fuel was clean and clear. Chucked it in my current 4X4 with no reported problems.

Caveat. The diesel was almost certainly too old to have any bio in it. When did bio start getting added? Currently B7, but was it B5 before that?

 

[KREW2]

We have a portable welder at our club which we used to use for mooring shackles. As we now reeve all our mooring chain it has been lying in our boat store for about 5 years. Due to a shortage of chain with large egg link and a desperate need to get moorings done ready for lift in we needed to do a little welding from our mooring boat.
I dragged it out, undid the fuel tap, diesel looked okay 8/10 pulls later it was running. Changed the oil, loaded it on the boat and it started first pull.

 

[Bilgediver]

Re-reading what I wrote, it seems like I'm saying that filtering is an option. No, I agree entirely that the fuel needs to be filtered.

One wee correction

It is not the air that is the problem. It is the fact that if there is air above the fuel and sometimes lots of it. Due to the effect of the diurnal range of temperature the tank effectively breathes in and out and each breath brings in more moisture trapped in the air, which is deposited in the tank as condensation and it is this moisture that the bug can t resist.

 

[Momac]

Take a fuel sample from the filter and see it is crystal clear like rose wine and change the filter
If there is a inspection hatch into the tank you might be ale to see if the fuel is clear
Give it a dose of fuel treatment and carry plenty of fuel filters on board .

 

[CAPTAIN FANTASTIC]

As other have suggested, filter it and use it. Also make sure that the bottom of the tank is clean and no sediment.

 

[TernVI]

It may or may not be OK.
I would get the fuel out, filter it and get the tank clean.
I'd avoid putting any additives in until the tank is clean.

You may find the tank is pretty clean, in which case just removing any dirt or water from the bottom is all you need.
I use a Pela to sample the bootom of the tank and remove any water.

If the fuel is clear and not cloudy, I'd be surprised if the engine did not run on it OK.
But as well as the bug, there is a risk of the fuel creating aspheltene (sp?) substances, other wise know as 'tarry blackshit' which can gum up pumps and injectors. For this reason, it's asking for trouble to store fuel for too long, but many people do so and get away with it.

No substitute for having a good look at it.

 

[Rappey]

The fuel could be proper marine diesel therefore have zero bio and be fine..

 

[Blueboatman]

Notwithstanding that the fuel could be treated already ....
I hate motoring off down the river with fuel uncertainties ..
To me , emptying the tank is a finite relatively straightforward effort whereas carrying around fuel uncertainty and all the other new-to-you boat ‘ unknowns’ is -to me- a bit too much open ended worry . For what ? Deferring inevitable maintenance ??
I would drain out the lot .
And store it/swap it /give it away /use on a drip feed diesel heater ..

 

[TernVI]

The fuel could be proper marine diesel therefore have zero bio and be fine..

Diesel bug was around long before bio diesel.
I had bug in red diesel 20 years ago.

 

[JumbleDuck]

It is not the air that is the problem. It is the fact that if there is air above the fuel especially lots of it. Due to the effect of the diurnal range of temperature the tank effectively breathes in and out and each breath brings in more moisture trapped in the air, which is deposited in the tank as condensation and it is this moisture that the bug can t resist.

This is much believed but unlikely to be true. Some numbers:

When 1 litre of air cools from 20C (293K) to 0C (273K) it reduces to 273/293 of its previous volume and so sucks in 20/293 litre of air from outside. Assuming that air is all at 20C and saturated, it has a moisture content of 17.3 mg per litre, so the maximum amount of water available to condense in the tank is 20/293 x 17.3 mg = 1.18 mg.

In other words, the maximum condensation you can expect from 1 litre of void space alternating between 0C and 20C is 1.18 mg per cycle. In practice it will be much less than this, but the sums are harder so let's stick with the worst case.

That means that a tank with 100 litres of air in in might in the worst case get 100 x 365 x 1.18 mg = 43 g of water over a year. That's probably (sticks finger in air, waggles it about) an overestimate by a factor of 10, so in reality somewhere around 4 g of water, or 1 teaspoons. The solubility limit for water in diesel is around 100 ppm, or 1 in 10,000, so those 4 g of water can be absorbed by 40 litres of fuel, even without additives.

It seems much more likely that the water in fuel comes with it, as a result of contamination in production, storage and transport.

 

[jwilson]

I once delivered a yacht that had a huge full tank of diesel, that had been ashore unused about 10 years. But that was with old red diesel, not the nasty modern mucked-about-with biodiesel.