David Rive
Senior Member
How long is diesel good for? The boat I bought in August has tanks (300 gal) that are 3/4 full. That fuel is on average probably 3 to 4 years old, based on what the previous owner has told me. Should I get rid of it?
Maximum Life of Diesel Fuel?
- Thread starter David Rive
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Capt.Bill11
Guru
What brand/model of engines do you have?
OP
OP
David Rive
Senior Member
Lehman 135s
MYTraveler
Guru
FWIW, I know of a mission-critical backup generator with enough fuel to run 24 hours a day for 7 days. Anyway, they change the fuel every 400 days (and pay to have the old fuel removed).
cappy208
Guru
You could hire a fuel polishing service. They come in and hook up their high capacity pumps and filter the fuel repeatedly. It takes out the growth that's happening in the tanks. If the tanks are really bad they will clean them too. Worst case scenario pay someone to take the fuel away. But that's pricey.
Have you checked if the boat already has a fuel polishing system? Some do. And in reality it's not that difficult to install one anyway.
Have you checked if the boat already has a fuel polishing system? Some do. And in reality it's not that difficult to install one anyway.
hollywood8118
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When we bought Volunteer the fuel was 3+ years old, I had 1000 gallons on board and I got rid of it by running it through the John Deere over the next 1-1/2 years. It did appear the soot up the transom a bit but not too bad. I bought a case of racor filters and went through a couple in the 1-1/2 years. I have heard that newer motors are touchy regarding fuel age but have seen nothing to back this up.
HOLLYWOOD
HOLLYWOOD
Capt.Bill11
Guru
Change your fuel filters, top the tank off with new fuel and use it. Add more new fuel as you burn down the old. Keep an eye on your filters.
I wouldn't spend the money on "polishing" the fuel unless it proves to be very contaminated.
I wouldn't spend the money on "polishing" the fuel unless it proves to be very contaminated.
AKDoug
Guru
I'm with Captain Bill. I would also add a good additive and make sure I had an extra set of filters on board, but I would use the fuel. My boat had 100 gallons of up to 10 year old diesel in it, only 46 hours on the engine, when I bought it. I had no idea how old the fuel REALLY was, so I pumped it dry and the boatyard used it in their shop heater. The first filter sludged up on the first tank I ran through it but has been clean ever since (3 years ago). I would be running short trips for a while with a new boat anyway while I built confidence in the engines and systems.
kapnd
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Take a sample before the filter into a clean glass.
If it looks crappy, call the polisher guy, or get rid of it, then get the tanks cleaned.
If it looks clear, try and run it.
Your Lehmann is much more likely to run on the stuff than a newfangled common rail electronic engine would be.
It can be mixed with new fuel to improve it, but should be used up asap.
If it looks crappy, call the polisher guy, or get rid of it, then get the tanks cleaned.
If it looks clear, try and run it.
Your Lehmann is much more likely to run on the stuff than a newfangled common rail electronic engine would be.
It can be mixed with new fuel to improve it, but should be used up asap.
cappy208
Guru
Unless you are confident in changing filters underway (and bleeding injectors) I would give serious consideration to having the fuel filtered (polished) and the tanks cleaned prior to use. It's not particularly difficult to change and bleed filters while away from a dock. But it IS nerve wracking for the guests! Or significant other.
Actually, the engine already acts as a 'polisher'. Diesels pump way more fuel than they burn. So they 'clean' the fuel them selves. BUT you will have to learn how to change filters. And having a vacuum gauge installed in the fuel line is necessary. You don't want the engine dying at an in opportune moment.
My Perkins burns about one GPH running. But the fuel pump pumps 8 Gallons an hour. Yours should be similar. Also, Rough weather will 'stir up' the sediment in the tanks which will hasten the filter clogging.
As far as the diesel being 'good': The combustible properties are fine. It is the contaminants that will be a problem clogging the filters.
Also, regarding filters. They are rated in 'Microns'. The smaller the number the less crud they let through (but the quicker they clog up). But be aware that even a fine filter can let a certain percentage of 'larger' crud through. So filters are a replacable, usable part of the fuel system. If you starve the engine for fuel (continue to run with clogged filters) you risk burning up the fuel injection pump.
Actually, the engine already acts as a 'polisher'. Diesels pump way more fuel than they burn. So they 'clean' the fuel them selves. BUT you will have to learn how to change filters. And having a vacuum gauge installed in the fuel line is necessary. You don't want the engine dying at an in opportune moment.
My Perkins burns about one GPH running. But the fuel pump pumps 8 Gallons an hour. Yours should be similar. Also, Rough weather will 'stir up' the sediment in the tanks which will hasten the filter clogging.
As far as the diesel being 'good': The combustible properties are fine. It is the contaminants that will be a problem clogging the filters.
Also, regarding filters. They are rated in 'Microns'. The smaller the number the less crud they let through (but the quicker they clog up). But be aware that even a fine filter can let a certain percentage of 'larger' crud through. So filters are a replacable, usable part of the fuel system. If you starve the engine for fuel (continue to run with clogged filters) you risk burning up the fuel injection pump.
This is actually an interesting question to which I have yet to find an adequate answer. A lot if us have fuel on our boats that is quite old. In doing a Google search, there is little real info out there. Most of what pops up is either from "Prepper" publications of one sort or another or from companies selling fuel additives. Neither of which were very authoritative. I even asked an acquaintance who is a petrochemical engineer for Chevron. He could not come up with any real experimental or scientific basis. He did say that Chevron "recommends" that any diesel kept for more than 30-60 days definitely needs some form of biocide or algaecide assed to it. It should also have a water mulsifier added to it to make the water condense out and fall to the bottom of the tank. According to him, Chevron does not recommend storing diesel for more than one year even with proper treatment. According to him, diesel does not really "degrade" such that it will no longer ignite or burn, but the little thingies growing, and the presence of water in the fuel, cause fuel systems to blow up. This happens more quickly with diesel that has any "bio-diesel" mixed with it. All of the literature I could find dealing with fuel management talks about water separation and fuel polishing to remove the microbial growth. And all seem to indicate, without saying so explicitly, that if fuel id kept clean of microbial growth and dry (ie. water condenste removed), it will pretty much last forever. This seems to be a very common question, especially among boaters, that has no real experimental or scientific basis to really answer. I would tend to take the approach, if you can be sure it is clean and dry, use it. Just pay attention to your engines and fuel system as you do.
cappy208
Guru
I have had more problems with adding biocides to tanks over the years versus just filtering the heck out of the fuel. The biocides kill the growth that then just falls to the bottom of the tank. Then rough weather stirs it all up clogging filters all over again. Constant, high volume filtering is the answer. The preventative measure would be to add biocide BEFORE the growth of the bacteria (a long period of disuse). But who has the foresight to do that!? We ALL want to use the boat as much as possible. To own a boat and not use it for years signals the end of ownership usually.
Liberty2015
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From reading the threads I have come to conclusion, that the best way forward is to use your boat ( a good start ) monitor your filters and do regular maintenance.
Sounds like a good plan to me . To try and cover every possible what if will start to drive you mad, so get out there and get moving!!
Chris D Liberty
Sounds like a good plan to me . To try and cover every possible what if will start to drive you mad, so get out there and get moving!!
Chris D Liberty
what_barnacles
Guru
I'd say no, Just filter it. With a 5 micron filter my 8 year old diesel looks brand new (to the eye). Going into the filter its black as coal and coming out its a clear red. If it's lost any potential, I cant tell at all.
You can get a big parker 1000 filter for close to a $100. That will let you burn the fuel and allow the filter to last quite a while. When you burn down the fuel just add another pump and use the filter for polishing the fresh fuel.
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BINGO!!! I would not add biocides!!! You will end up with a long term problem with crap in your tanks. I would either remove it or use it but don't "shock" the tank with biocides.
Just use it and watch and change filters as needed. Do not add additives as they may cause any suspended stuff to drop to the bottom. Don't add new fuel either.
You want to use up the old fuel ASAP but adding new fuel just dilutes the old and you will never get totally rid of it. Run the tanks down than add a little and run them down again is the fastest way to get rid of the old fuel. Low fuel sloshing in a sea way will also stir up junk to allow filter to do their job.
Old fuel may not have as high a cetane level as new but unless you are running high power engines at max load it wont matter.
You want to use up the old fuel ASAP but adding new fuel just dilutes the old and you will never get totally rid of it. Run the tanks down than add a little and run them down again is the fastest way to get rid of the old fuel. Low fuel sloshing in a sea way will also stir up junk to allow filter to do their job.
Old fuel may not have as high a cetane level as new but unless you are running high power engines at max load it wont matter.
Old deckhand
Guru
I transfer a boat with 6 year old fuel 200 miles with a 275 hp 3208 cat. No problems.
Panope
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I foolishly gave away 12 year old deisel that looked, smelled and worked perfectly. Boat was on the hard. Tanks were 1/4 full. No biocide, no bugs, no condensation.
My friend happily used the fuel in his truck.
I let paranoia get the best of me.
Steve
My friend happily used the fuel in his truck.
I let paranoia get the best of me.
Steve
Ski in NC
Technical Guru
I too have been "donated" old diesel fuel from folks that consider it "too old" to use. I mix it with new, maybe 50/50, then use it in my machines. Never had a problem. Some was over ten years old.
Phil Fill
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The old high sulfur and no bio would last decades. However most diesel today is low sulfur and does not last as long. The length of time depends on your location and if your main engine, gen set and diesel heat polish the fuel, or if you polish the fuel. Most diesel engine draw more fuel than the use, so do heaters. So the polish the fuel while the run. Our, main 671 draws 50+gallon but use max 5 gph. Thus 40 gallons are returned to the tank clean polished. Most large fuel tank long range boats have fuel polish systems. So we can sit at the dock and polish the fuel.
Its water moisture in the tank and the fuel separating out out that is the cause of algae bugs. So I add additives that absorb the water moisture back in the fuel and the additve wil
Prevent separating, tarring. So if depends on you boat, area, and prevent mrasures you use.
If you are concerned might want to have double filters, so it a filter is bad, you can switch over to a new filter and replace the old while the engine is running. Best to have vacuum gauges on the filter so you can monitor the fuel filters.
Its water moisture in the tank and the fuel separating out out that is the cause of algae bugs. So I add additives that absorb the water moisture back in the fuel and the additve wil
Prevent separating, tarring. So if depends on you boat, area, and prevent mrasures you use.
If you are concerned might want to have double filters, so it a filter is bad, you can switch over to a new filter and replace the old while the engine is running. Best to have vacuum gauges on the filter so you can monitor the fuel filters.
Last edited:
OP
OP
David Rive
Senior Member
Interesting discussion, I appreciate all the input. One thing I neglected to mention is that this winter (she was just hauled) I am replacing the original fuel tanks.
I think after listening to everyone's comments I will have the fuel professionally polished (assuming the cost is not crazy) and then pump it back into my shiny new fuel tanks and use it next summer.
I think after listening to everyone's comments I will have the fuel professionally polished (assuming the cost is not crazy) and then pump it back into my shiny new fuel tanks and use it next summer.
Well, I woke up this morning to an email from my petro engineer friend (he is in Indonesia so he must have had a boring work day to send all of it to me) explaining what the little microbes do and their effect on diesel. He even included a PHD Thesis he found by some guy at Texas Tech explaining the whole process, most of which I am not capable of understanding. But a summary of what he explained to me:
The microbes are naturally occurring bacteria that feed on the carbon in the diesel hydrocarbon molecule. They consume the carbon, using relatively vast (for them) amounts of oxygen, thus breaking up the diesel hydrocarbon molecule and leaving hydrogen behind which will either evaporate or combine with the oxygen to make water. Apparently, this is a very slow process. These bacteria have been used to clean up oil leeched into the soil in spills, but because it is slow, it is not all that effective. The long and short of it is that the bacteria are eating your fuel! If left long enough, they will consume all the available carbon, become a huge soggy organic mess, and die off and you have a ruined tank and no fuel. That said, that would take a very, very long time. This is a naturally occurring process that begins as soon as fuel leaves the refinery. Hence the need for fuel filters. His opinion finally was that fuel treated with a biocide and filtered (polished) regularly would essentially last forever although whatever growth there may be between filterings will be eating away very tiny, tiny amounts of your fuel volume. There is nothing in the chemistry of diesel fuel itself that causes it to "degrade" losing its ability to ignite and combust. According to him the hydrocarbon bond in diesel is one of the stronger chemical bonds (which explains big refineries!). Hope most of this makes more sense to some of you than to me.
The microbes are naturally occurring bacteria that feed on the carbon in the diesel hydrocarbon molecule. They consume the carbon, using relatively vast (for them) amounts of oxygen, thus breaking up the diesel hydrocarbon molecule and leaving hydrogen behind which will either evaporate or combine with the oxygen to make water. Apparently, this is a very slow process. These bacteria have been used to clean up oil leeched into the soil in spills, but because it is slow, it is not all that effective. The long and short of it is that the bacteria are eating your fuel! If left long enough, they will consume all the available carbon, become a huge soggy organic mess, and die off and you have a ruined tank and no fuel. That said, that would take a very, very long time. This is a naturally occurring process that begins as soon as fuel leaves the refinery. Hence the need for fuel filters. His opinion finally was that fuel treated with a biocide and filtered (polished) regularly would essentially last forever although whatever growth there may be between filterings will be eating away very tiny, tiny amounts of your fuel volume. There is nothing in the chemistry of diesel fuel itself that causes it to "degrade" losing its ability to ignite and combust. According to him the hydrocarbon bond in diesel is one of the stronger chemical bonds (which explains big refineries!). Hope most of this makes more sense to some of you than to me.
C lectric
Guru
It might be worth considering sending a sample of the fuel to an oil testing lab. Many labs also test fuel for contamination. For ~$40 it would be worth it with the fuel quantity you have.
Lehmans, to my knowledge, do NOT pump a large quantity of fuel beyond what they use. There is some excess but unlike some engines there is not a lot of return fuel so the engine itself is not terribly effective as a polisher.
For confirmation one way or the other try contacting American Diesel who are the gurus of these engines.
American Diesel Corp
Lehmans, to my knowledge, do NOT pump a large quantity of fuel beyond what they use. There is some excess but unlike some engines there is not a lot of return fuel so the engine itself is not terribly effective as a polisher.
For confirmation one way or the other try contacting American Diesel who are the gurus of these engines.
American Diesel Corp
CPseudonym
Moderator Emeritus
Me too, gas, diesel and kerosene.
Any of you Northern California members looking to donate old fuel just shoot me a PM.
Bay Pelican
Moderator Emeritus
Fuel polishing on the simple. Get either a Gulf Coast Filter or a Racor and add a Walbro FRB-13 pump to pull the fuel through the filter. Add a couple of ball valves and hose tees so you can draw fuel from before the primary filter and return it after the engine. You can then when at rest draw the fuel from the tank pull it through the filter and then back to the tank. Underway you close the ball values and the polishing system is not interfering with your fuel system.
cappy208
Guru
It's simple. The fuel in the tanks is at most 6 months old. The fuel being discussed here is anywhere from a year to several years old.
The inground tanks stay relatively cool which inhibits the bio growth. There's a big difference between shoreside fuel tanks and ones on boats.
The absolute worst fuel tanks are on boats down south that get hauled out on lifts for months at a whack and the fuel gets to 80 90 or higher in the tanks with engines that don't get run periodically to circulate the fuel to clean it up.
