Shelf Life of Diesel Fuel

[pjfsail]

Does anybody have any FACTS on the shelf life of diesel fuel? I looked on the web and the estimate varies from 1 year to infinity. I'm sure it is somewhere inbetween and probably a lot of factors come into play. It would be interesting to hear some facts. Anybody got any?

[s/v Beth]

An important part of preserving diesel fuel is keeping it dry and clean. The navy polishes their fuel continuously while in port, and I have never hear of them having to dump fuel that is old. The problem is not that diesel breaks down - algae grows in it if there is water around and clogs the system. As you can imagine, it is hard to keep water out of a tank of a boat in the water. Thus the need for cleaning.

[CalebD]

I believe that newt hit the right nail on the head on this one. Diesel fuel is more like an oil then gasoline which has a much shorter 'shelf' life given the same conditions.
Once water gets into diesel fuel bacteria/algea can grow in the tank and leave you with all kinds of problems. Another potential problem is taking on fuel from a source that may have water/algea in it. Hence the need for fuel polishing pumps, filters etc.
Diesel fuel should last a long time if it is kept clean and dry unlike E10 gasoline which actually tends to trap water in it over time.
Age of the fuel should not be an issue if the tank(s) are kept clean and dry and the fuel source is also clean.

[anjou]

In UK, non road use diesel is dyed red as its sold at only 5% duty and no VAT. Since November last year, its now only permitted to be used as heating and stationary fuel, not for cruising on water. This diesel is mainly for agricultural and heavy industrial use, hence the reduced duty rate and its got a higher sulphur content and certainly doesnt deliver as much energy as road fuel.

I was told that the sulphur improves its shelf life qualities even though it adds to the coking/carbonising problems associated with combustion.

[Talbot]

Originally Posted by newt

An important part of preserving diesel fuel is keeping it dry and clean. The navy polishes their fuel continuously while in port, and I have never hear of them having to dump fuel that is old. The problem is not that diesel breaks down - algae grows in it if there is water around and clogs the system. As you can imagine, it is hard to keep water out of a tank of a boat in the water. Thus the need for cleaning.

UK warships actually use water compensating fuel tanks, so the fuel is replaced by seawater as it is used. This obviates any centre of gravity problems as fuel is uded up (actually the ship gets heavier!)

It also means that the first stage of sucking fuel is to scavenge the water from it anyway.

[mesquaukee]

A acquaintance of mine on a 65 foot trawler once every 5 years or so goes to Venezuela and fills up with 8,000 gallons of diesel. He adds 100 gallons of gasoline to it. Then he comes back to Panama and Columbia and cruises for 5 years on it.
Never uses biocide, he says the gasoline kills it. He used to be a professional fisherman.

[Tampabayfireman]

I dont think i would mix the two.. I have always heard it only takes a small amount to contaminate the deisel fuel, and the damage to the engine is highly likely....

[mesquaukee]

Originally Posted by Tampabayfireman

I dont think i would mix the two.. I have always heard it only takes a small amount to contaminate the deisel fuel, and the damage to the engine is highly likely....

Years ago I had a diesel car in the Great White North and in the winter you had to add up to 10% gasoline according to the owners manual. Below 0F it would start to gell up in the fuel lines etc.
At -40F I found I had to add up to 15% gasoline. It did not seem to change the performance much!

[r.furborough]

On the contrary, gasoline used to be added to diesel fuel during the winter months by truck dirvers to prevent waxing, it used to be common practice and if used in moderation caused no engine damage.

[DWT]

I have a 15 KW diesel generator for the house here in south Florida for the hurricane season. I fill it up( 33gal.) every year at the beginning of hurricane season and if I am lucky I have alot to take out of the generator and put into the sailboat at the end of hurricane season/ begining of sailing season. By turning the fuel over you keep it fresh and I have had no problems with fuel jelling on me....works for me!

[zeehag]

my yanmar in my ericson is only used infrequently andf my diesel has had additive to prevent growth of gunk in my tanks--has been 3 years since i filled tanks and i still have half tank--works well even in choppy waters----go figger......we will see how well the diesel that has lived in my formosa for 5 yrs will behave...lol--has had same additive so i believe it will be fine.....

[s/v Beth]

I have not heard of adding Gas to Diesel, I do have some anti-fungal additive that I am going to put down the tank. Practical Sailor did a pretty good article on additives last month. It should still be online for those that are interested. (I ended up with the Racor product)
I am now just installing new fuel lines, and I am going to put a polisher in my Valiant.

[sundown]

For what it is worth I have 3 year old diesel in my tanks. 4 days ago I started to take the boat out for an evening sail/ motor (there was no wind) and just cleared the harbour and the engine quit! In two weeks I had gone from a clear sight glass to opaque. I am totally amazed at how quickly the algae "bloomed" . Now I am stuck with the job of trying to find someplace to get rid of 40 gal of contaminated fuel.
The lesson I have learned: Put biocide in the diesel - it is cheap insurance.

[speedoo]

Originally Posted by sundown

For what it is worth I have 3 year old diesel in my tanks. 4 days ago I started to take the boat out for an evening sail/ motor (there was no wind) and just cleared the harbour and the engine quit! In two weeks I had gone from a clear sight glass to opaque. I am totally amazed at how quickly the algae "bloomed" . Now I am stuck with the job of trying to find someplace to get rid of 40 gal of contaminated fuel.
The lesson I have learned: Put biocide in the diesel - it is cheap insurance.

Try getting someone to polish your fuel. Probably a much better option than getting rid of it.

[s/v Jedi]

You can polish it yourself. Disconnect fuel feed hose from engine and connect it to a small pump (like those cheap impeller pumps you put in your electric drill). First, pump a gallon into a bucket and then switch to an empty tank, jerry jugs or even back into the same tank (deck fill). When the flow stops, replace the filter cartridge in the primary filter with a new one and toss the clogged one in the bucket. When it clogs again, flop the filter element in the bucket around a bit and put it to use again, alternating between the two elements as you go.

When you pump back into the same tank, you have to circulate 5 times the amount of fuel that's in the tank, so time how long it takes to pump that first gallon.

You can get unlucky when the pick-up tube in the tank is clogged. You have to remove the tube to clean it and I would advice to remove any mesh strainer it has (let the primary filter deal with filtering).

We have a fixed (self designed and installed) installation for that, plus the ability to drain from the bottom of the tanks. I first drain a little in a glass jar to check for water (and drain it all when I find it) before filtering. The fixed setup uses a seperate Racor 500 filter for this, plus a little Walbro pump. See s/v Jedi: A new fuel system for Jedi (English) for a complete description, photo's etc. When you build this yourself the cost is the Racor filter and the pump(s) (I use two pumps, one for bleeding/priming/boosting).

cheers,
Nick.