Old diesel dilemna

[stranded]

After mostly successfully sticking to my resolution only to use the engine for in and out of harbour, I find myself with over 100 litres of 18 month old fuel left in the 240l tank. Use will be even lower over winter, then similar next year.

Is continuing to use fuel of that age likely to cause problems with the aux. or generator engines, or the heating?

If not, I could use it up then put less in next time. But what about increased condensation in an emptying tank - is that a major risk or a marginal one?

So maybe I should top up the tank and dilute the dodgy diesel. But I’d have to do the same next year, and so on, with traces of ever older diesel always in the mix. That doesn’t sound like a good idea?

If neither is good long term, is there a relatively straightforward way to divide the existing tank to create a smaller subtank while keeping the full capacity available for when we head overseas again? The tank is stainless steel, under the aft bunk, all of the top and about 3” of three sides are accessible (eg for cutting the lid off) without dismantling the furniture. I’d be getting a pro to do it.
Must be a common problem, which suggests I may be wondering too much, but thoughts or suggestions would be most welcome.

 

[Pete7]

I doubt anyone will want to weld a tank that hasn't been flushed out and dried, particularly inside a boat. If the tank won't come out easily, I would leave well alone and just dowse with your preferred bug killer.

Pete

 

[TernVI]

Condensation is largely mythical.
Personally I would check the bottom of the tank for dirt and water, we do this a couple of times a season. We just take a couple of litres out with a Pela. Heel the boat to take it from the low side.
There's always a few droplets of water, same as there usually is in the float bowl of the outboard carb.

I don't think fuel keeps like it used to, I like the idea that in Spring we will buy some fuel and know that what's in the tank is 90% new.

 

[Biggles Wader]

I use marine 16 and keep my tank nearly empty most of the time. I do have a sump with a drain tap to ensure no water is present but have had no problems (touch wood) since a clean out four years ago. Id just treat and carry on.

 

[stranded]

Threes a quorum in my book, so that’s unanimous then - I shall use up some more over winter and then take on less in future - always use Marine 16 anyway. Thanks for the replies.

 

[Topcat47]

If you have (white) road diesel in the tank, it's got 5% ethanol in it. Ethanol is hydroscopic (it absorbs water) and doesn't age well. It also attacks a lot of traditional sealing materials. If you have "proper" diesel, it will be low sulphur mineral oil with a few additives. "Propper" Diesel is fine and doesn't "age". Any water that gets into the tank will sit at the bottom, so siphoning out a pint or so should prevent proliferation of the dreaded "bug". A liberal dose of biocide will help kill off any residual bacteria. If you find black sludge in the bottom of the tank, too late, you have to clean the tank properly as this stuff causes all sorts of problems when it gets into the fuel lines. (I didn't say "if"). I have a tiny "sump in my fuel tank and there is usually a red powdery deposit here that appears in a clear siphon. I had mine tested in a lab when I first noticed it and it was residue from the red dye used to colour the diesel, together with some "fine inert particulates". (AKA dirt in the fuel)

Last time I had the dreaded "bug" I removed the tank and had it steam cleaned. It then leaked and I had to have to out, steam cleaned and welded up (it's SS). I should have had it tested when it was first cleaned. Lessons learned. I filled the tank two years ago at the end of winter. This year the boat has hardly moved from it's mooring, yet the engine started immediately when I was hauling out.

Condensation is not mythical. Metal tanks get cold in winter and any moisture in the air space will have vapour in it which will condense out as the temperature drops. This is why boat owners are often encouraged to top up at the end of the season. You never get much but it will permeate to the bottom of the tank and pool at the lowest point. Make sure your filler cap seals well, moisture more often gets in when it rains and this will be a bigger concern. I try to ensure my boat is propped up a little down at the bows and slightly listing to encourage rain water away from the filler as well. I also smear a little sealant (blue hylomar or Fernox LSX) around the edge of the filler cap as it's almost flush with my deck. The sealant is easily removed in the spring.

You won't get an engineer to weld a fuel tank that hasn't been cleaned and some will insist it be purged. Good HSAW practise.

 

[convey]

What do you use for heating, an Eberspacher type?

I'd be tempted to put in a separate header tank for fresh day to day engine work. Many folks with Refleks style heaters etc use a smaller, separate, pump fed header tank just for them but that's more about getting sufficient head height for it.

I don't know Eberspacher but I plan on running old fuel through the Refleks. Figure it's so basic, it's hardly likely to care.

 

[stranded]

Thank you for the further info. The boat did have a separate ‘day tank’ when we bought her - about 50l I guess - but I had it taken out because it was a tight fit under the helm seat and made the back of my calves cold when I was standing at the wheel! Subsequently had the helm seat removed as well so I’d have to find another position.

Going off the wall somewhat, what about putting some fuel tank equivalents of bricks in the toilet sistern to reduce capacity - plastic footballs or something?

 

[convey]

I like overthinking things, but also fresh fuel. How much do you think you use on a regular basis? In and out with a little for emergencies.

You get typical bilge style pumps for hand pumping fuel from one tank to another.

Has anyone adapted or adopted bladdered expansion style tanks, like those used for gas/heating systems, to marine/diesel use?

 

[TernVI]

Also bear in mind that most of the anti-bug additive makers state that treated fuel should be used within months.

 

[Rappey]

Proper" Diesel is fine and doesn't "age

The problem there is finding marine diesel.
I read an article explaining the 3 types of red available.
The one starting with a BS number was the real stuff, by definition it was not allowed to contain any bio fuel.
The other two were both EN numbers which can contain 4.5% to 10% bio fuel.
Both can be sold as marine diesel.
I rang around the local fuel outlets and non of them knew what red they were selling.
Premier told me their fuel contains an additive but could not tell me if it contained bio diesel.
I have used their fuel for 30 yrs and have never had a problem yet which is good as I have a large tank in the keel and rarely use over a 1/3 of it per year.

 

[neil1967]

We have a 500 litre tank in a sailing yacht and use very little - we spent 3 years in the Netherlands and did not put any fuel in until just before we left. We had no problems at all. I think the diesel 'problem' is over stated - just keep the tanks clean, dose them occasionally, and go sailing.

 

[Graham376]

We have a 500 litre tank in a sailing yacht and use very little - we spent 3 years in the Netherlands and did not put any fuel in until just before we left. We had no problems at all. I think the diesel 'problem' is over stated - just keep the tanks clean, dose them occasionally, and go sailing.

+1

My tank contends are at minimum of 2 years old and some of the mix will be 3 or 4 years. Starts and runs fine, I just dose with Fuel Set each time I top up.

 

[stranded]

I like overthinking things, but also fresh fuel. How much do you think you use on a regular basis? In and out with a little for emergencies.

You get typical bilge style pumps for hand pumping fuel from one tank to another.

Has anyone adapted or adopted bladdered expansion style tanks, like those used for gas/heating systems, to marine/diesel use?

I reckon we will use about 100l a year - hard to know because the engine austerity was a reaction to far to much motoring en route to, in, and en route back from, the med. Being based in SW UK is new to us and I hope this year will not prove to have been typical! If the condensation thing really is marginal (by following the excellent advice re keeping the tank clean), happy to run on fumes so long as I make sure my 20 litre Jerry can is kept full and fresh.

 

[[70521]]

"Propper" Diesel is fine and doesn't "age".

I'd be interested where you can get this "propper" diesel.

I had a dose of the fuel bug a few years back when I was using red. I strongly suspect that the turn over at the garage, we live in rural Devon and such things do exist, was not large. Since then I've used garage white and not had a problem. I never fill my tank up, perhaps it is the Scot in me, but why have all that cash sloshing about in your tank. So far I've not had an issue with condensation. The tank is due to be removed, cleaned and inspect next winter during the boat's three year lift out.

 

[Topcat47]

1. Cowes Harbour commissioners fuel barge, just past the chain ferry does Marine Diesel with no Methanol.

2. The bug lives and grows in the interface between diesel and water. For you to have a bug problem you have to have water in the tank. Methanol in Diesel isn't a problem in motor vehicles because of the high turn over of fuel (My Rav4 uses a tankful every two or three weeks) My yacht seldom burns more than 25 litre as season, 35 in a good year (last year probably only about 1-2 litres). The tank holds 44. Were I using "White" Diesel I'd pump out the fuel tank and use it in the car, filling up at the start of the season and put a box of Dessicant in the tank while the boat's ashore. I've had three bouts of the bug and am not keen to have a fourth.

I suspect if you're using garage white, the methanol in the fuel will absorb any condensation but it does "go off". Adding fresh fuel means that you'll enrich the old fuel when you do it, but wouldn't like to rely on it. I suspect my old 1GM10 isn't critical when it comes to fuel quality anyway. I've a mate who uses road diesel in his boat but he buys the premium stuff from Shell or BP believing the extra additives help. I no longer have access to a fuel testing lab and have never explored the phenomenon.

 

[[70521]]

1. Cowes Harbour commissioners fuel barge, just past the chain ferry does Marine Diesel with no Methanol.

That's a bit far from Plymouth for 20 ltrs of fuel.

2. The bug lives and grows in the interface between diesel and water. For you to have a bug problem you have to have water in the tank. Methanol in Diesel isn't a problem in motor vehicles because of the high turn over of fuel (My Rav4 uses a tankful every two or three weeks) My yacht seldom burns more than 25 litre as season, 35 in a good year (last year probably only about 1-2 litres). The tank holds 44. Were I using "White" Diesel I'd pump out the fuel tank and use it in the car, filling up at the start of the season and put a box of Dessicant in the tank while the boat's ashore. I've had three bouts of the bug and am not keen to have a fourth.

It must have been well dispersed water, as none was found when we stripped the system down. Just a horrid jelly clogging up the primary filter.

I must introduce you to some of the diesel fitters I used to work with they have stories of the fuel bug in lorries and other heavy plant.

One of the reasons for moving to white was that I could use it in the car. 10 lts were decanted from the tank and transferred into the old jalopy, why more people don't do this is beyond me, oh hang one they are using that red stuff.

 

[Spirit (of Glenans)]

I've got oil-fired central heating at home. It uses kerosene, but but adding modest amounts of green diesel removed from my boat's tank has caused no ill effects when added to an almost full tank of kerosene. Those whose boilers use Marked Gas Oil can of course add any amount of boat diesel.
I should add, in deference to the OP's question, that I haven't had to do this in recent years, as due to a number of circumstances, I have only recently used the last of a tankful of diesel that I filled up in 2014. There was no detectable loss of performance, or evidence of "going off", so IMHO, using old fuel shouldn't be a cause for concern.

 

[Neil_Y]

If you're ever left with diesel to get rid of, try your local garage, mine was happy to use it in their hot air heater .

 

[Graham376]

I suspect if you're using garage white, the methanol in the fuel will absorb any condensation but it does "go off".

In common with tens of thousands of EU boaters, we're using road white and haven't had a problem. Why do I see and hear of far fewer cases of bug than in UK? Is it down to UK storage conditions?