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Old diesel fuel

Discussion in 'Ask All Sailors' started by pelicanj45, Jun 22, 2014. Add this thread to a FAQ

  1. pelicanj45


    Joined Jul 17, 2012
    38 posts, 0 likes
    Hunter 36
    US AuGres MI
    I have about 3/4 tank of diesel fuel. It’s all of five years old. Only been day-sailing so very little fuel has been used.

    I've been thinking of draining it. I hear horror stories of algae growing in the tank and getting into the injector system. I put Sta-bil in it every fall so I wonder, do I drain or not? Any suggestions??

    The way I see it, it'll have to be taken out in gallon jugs. Even if I do drain it, how and with what do I clean the tank?

    Thx, Pelican

  2. Steve Dion

    Steve Dion

    Joined Dec 2, 1999
    15,181 posts, 10 likes
    Hunter Vision-36
    US Rio Vista, CA.
    If you are concerned you can just try sucking the junk off the bottom of the tank If there is any water & algae it is on the bottom.

    Suck it out and put the stuff in a glass jar to determine if there is any junk in the tank.

  3. Ralph Johnstone

    Ralph Johnstone

    Joined Jan 4, 2006
    2,436 posts, 268 likes
    Hunter H-310
    CA West Vancouver, B.C.
    Here's a report for some fuel to a standby generator which I had analysed at six years of age and was still listed as good to go. According to the lab, as long as it's dry and clean, they don't know how many years it will last.

    I would follow Seve's recommendations as a minimum.

    Attached Files:

  4. sailor2002


    Joined Jan 28, 2013
    4 posts, 0 likes
    pearson p-38
    US old saybrook
    Diesel is stable by nature of its chemical properties

    Diesel has only one enemy. That is moisture. Dry diesel should last 10 years or more.
    However I found that Diesel is not always as pure as we like to think. So I would recommend Startron Diesel additive. (blue bottle) my experience over 8 years with the stuff is that it works, well. There are many other additives, most do not work on the molecular level to bind moisture and odd radicals that cause sedimentation in Diesel.
    Algae comes from the introduction of rain water or water that has the algae in it. From the fuel station? over time it grows as a sludge.
    Startron will not treat Diesel once it has the sludge. Only prevents it. However once the tank is empty after an issue, startron has a tank clean formula that will help clean out the small left overs.
    thanks hope this helps.

  5. Stargazer3


    Joined Feb 21, 2011
    69 posts, 1 likes
    Hunter 410
    US Lorain
    I agree with Steve. Stick a tube into the access hole on top of the tank & suck some fuel off the bottom. If it looks ok - you good to go. I use a biocide & stabalizer every fall at haul-out - and it seems to be doing the trick. Never had any problems. Capt Bill on STARGAZER

  6. jmce1587


    Joined Mar 20, 2011
    293 posts, 37 likes
    Hunter 31_83-87
    US Kemah
    Another possibility is using a fuel maintenance company in your area. They can polish the fuel and return it to the tank and clean the tank while polishing and analyze fuel samples. had this done last week on my 2GMF as engine quit running due to dirty fuel/water contamination. took about an hour from set up to cleaning. fuel that came out of tank was dark ice tea looking with a lot of crud/water. I change filters annually only purchase fuel from a local marine fuel dock that uses biocide but with minimal engine use, it can become contaminated.

  7. Don S/V ILLusion

    Don S/V ILLusion

    Joined Sep 25, 2008
    5,145 posts, 324 likes
    Alden 50
    US Sarasota, Florida
    FWIW, diesel ages just like any other petroleum fuel. Less so than gasoline but API studies indicate diesel ages after 6 months; quicker depending on ambient temp and moisture. They also suggest the only additive necessary even for new fuel is a cetane booster.

  8. cygnussailor


    Joined Jun 2, 2004
    44 posts, 2 likes
    Catalina 400
    US Muskegon, Michigan
    I've only had problems with algae once. That was before I started using biocide. I see you are in Michigan. One of the ways to get moisture in your diesel is to leave your tank partially full during lay-up. With the extreme changes of temperature we have in Michigan the tank will warm and cool many times over the winter. This will cause moisture to be drawn in during the cooling phases and it can condense on the exposed tanks walls and get into the diesel. Your tank should always be full during winter lay-up with biocide and stabilizer added.

  9. zeehag


    Joined Mar 26, 2009
    3,193 posts, 31 likes
    1976 formosa 41 yankee clipper
    US santa barbara. ca.(not there)
    polish it yourself. save more than 300 usd.. polishing is filtering it and filtering it. then mix it with new and use. add bio bor. will work

    when i bought this boat i am cruising, it had a half tank of oold diesel from 5 or so years. worked fine.

  10. cooler


    Joined Jun 3, 2004
    4 posts, 0 likes
    - -
    US winthrop harbor
    for a few dollars more

    It's Sunday night, dusk. Sailing all day long, pulling back into home port of Winthrop Harbor. Sails down, engine running smoothly. Reach the mouth of harbor, engine stops. So suddenly, we check for a line on the prop, something. Crank engine, nothing. Anchor immediately. Avoid breakwater. Get a tow in to the mechanic.

    It was the diesel. The storage yard had failed to remove the old and put in fresh (they had billed me for it but not done it; they did own up to it and took care of us), and it fouled the engine.

    Theories about why diesel goes bad, and how long it will last in a lab go out the window at times like this, and the only thought once in port is why worry about saving thirty dollars worth of fuel on a sixty thousand dollar boat with my whole family on board?

    I go two years. I use less fuel in two years than some guys do getting to the gas dock, but I don't care. Out it goes, fresh goes in, and for the cost of a quart of bottom paint life is good.

    For about a year, the remains of a boat that had fetched up on the breakwater was sitting out on the grass at the yard. The deck, part of the cabintop, some lifelines. It suffered the fate we would have if we were not prepared with an anchor, etc. It served as a cautionary tale, for those who pay attention.

  11. barrylab


    Joined May 15, 2011
    1 posts, 0 likes
    Pearson 365
    US No. Weymouth, MA
    I bought a boat that had been on the hard for 5 years with a full tank (50 gallons) of stale diesel. I hired a fuel polishing company, and he cleaned the tank and polished the fuel for $250 dollars. Yes, I could have "polished it myself" but I don't own a high flow rate pump and industrial fuel filter.

    Let me explain:
    He drained all but about 10 gallons into a plastic drum he brought with him, then proceeded to power wash the inside of the tank with the high flow rate/high pressure pumping system and a metal wand that could be bent to reach all corners of the fuel tank. His pickup tube was placed in one port, and the spray end in the other (fuel siphon and return ports). He reversed them half way through the 30 minute exercise.
    His industrial filtering system included a large sock like cloth bag that captured about a gallon of black sludge that was apparently the microbes that grow in the presence of water. If you don't "power wash the internals with a lot of agitation, this sludge could come loose in a rough sea, and plug the fuel filters. I believe it's necessary to add a cetane booster and a lubricity booster to old diesel. By the way I use about 20 gallons a season, and change my filters every season. I've had no problems with the 38 year old engine that have to do with fuel. (water pump problems, oil leaks, and a rusted out exhaust system though).

  12. Capt. JG

    Capt. JG

    Joined Dec 24, 2008
    5 posts, 0 likes
    Sabre Mk II
    US Brickyard Cove, Richmond, CA
    Old diesel fuel is fine

    The best advice I had from a diesel mechanic is to not worry about it overly much. I'm in the same situation of not using my engine all that much. His recommendations were

    1) run the engine more (would you rather spend $50 in fuel or $8000 on a replacement engine?)

    2) if you haven't had a problem with dirty fuel, you don't have a problem, so don't fix what isn't broken. Your filter (assuming you've changed it) will deal with debris and show if you have water (at the bottom of the glass bowl on the filter).

    I run my engine (Westerbeke 13) hard at least once per outing whether I really need to or not. Diesels like to be run hard with little warm up.

    I hope this helps.


  13. scottthardin


    Joined Mar 22, 2010
    18 posts, 0 likes
    Beneteau 343
    US Lake Lewisville
    Using your sailboat as often as possible including just under power to burn the fuel down is more fun than polishing.

  14. tailwind


    Joined Jan 22, 2008
    53 posts, 1 likes
    Macgregor 21
    US MN
    I'd be as much worried about all the biocide/additives you are dumping in every year.

    NYSail likes this.
  15. bananabender56


    Joined Oct 3, 2011
    75 posts, 0 likes
    Tayana 52
    US Jax
    A potentially greater problem with the algae is the prospect of sulphur reducing bacteria. I understand the bacteria can remove the sulphur from steel and with the water at the tank bottom creates sulphuric acid, eating out the bottom of the tank.

  16. beeryboats


    Joined Jul 26, 2006
    25 posts, 0 likes
    - -
    US Eagle Creek
    I work at a diesel pump, injector, and turbo shop where we overhaul these components. We've found this new ultra low sulfur fuel really sucks. The older diesels seem to cope pretty well, but the newer common rail injectors start to fail fast if the fuel is not doctored up with additive. After six months we start to see internal pump parts start to gum up and stick. I'm in Indiana were we don't see many diesel boats, but the farm equipment that gets put away for the winter will most likely have issues if the fuel is not treated. I recommend Stanadyne Performance Formula. It's made by the same folks that have building the injection pumps for decades. And always keep the tank topped off to avoid condensation from raining inside the tank.

  17. 3rdbase


    Joined Jun 23, 2014
    9 posts, 0 likes
    IONA 30
    US CT
    Periodically, I start the engine to charge the battery. This allows me to use up some of the fuel over time. I also use the diesel biocide (Bio-Kleen) additive as well as normal Sta-bil. Knock on wood, I've never had a problem.

  18. Warren Milberg

    Warren Milberg

    Joined Dec 1, 1999
    2,356 posts, 96 likes
    Hunter 28.5
    US Chesapeake Bay
    I, for one, would never spend good money to polish old diesel fuel. It's like polishing a turd: you wind up with a nice, shiny, turd. Get rid of the old fuel if you question its quality. Alternatively, you can learn a lot about the quality of your diesel just by looking at it. Syphon out 8 or so ounces into a clear glass jar. See if there is a water layer. See if you have critters -- or any debris -- doing the backstroke in it. And look at the color. If it looks like iced tea it probably is iced tea. It should be clear and have a slightly greenish tint. Anything darker and the fuel has deteriorated. Why would anyone spend more to polish old fuel than what new fuel costs?

  19. nutheastah


    Joined Apr 3, 2008
    15 posts, 0 likes
    Lancer 28
    US spencer
    Diesel fuel should be replaced each year!!! or sooner. Algae will develop in it after only a few months and will become a nightmare to remove. It can float at the same buoyancy as the fuel, clog a line and when the engine shuts down float back into the fuel waiting to haunt you another day. you can drain the tank of all fuel and the algae can cling to the side of the tank only to haunt the next supply of fuel (it can easily plug a 3/8 inch fuel pipe). Todays diesel with its " environmentally safe ?" additives is no match for algae. all those things that prevented algae like sulfur etc. which use to be in fuel are gone. If it were my diesel in my boat I would keep a record near the tank noting when and how much I had fueled up. At the end of the season you can either drain your tank and give the old fuel to someone who burns waste oil or fill it to the top, both solutions have drawbacks but if your boat is on the hard for the winter 4 or 5 months can go by before the fuel is to be used again. I personally go for an empty tank and take a chance on a little rust in my filters There are additives to help prevent algae however someone else who is used them and has a handle on how effective they are would have to comment. The only additive I have ever used is ATF to help the injectors. Stale diesel is a good way to turn a good day to bad. I have 50 plus years as a diesel mechanic and I have made a lot of money resolving stale fuel in all kinds of diesel equipment. Also remember algae just loves the salt sea air.

  20. Blakem


    Joined Mar 12, 2012
    3 posts, 1 likes
    Oday 28
    US Glastonbury, CT.

    I agree that petroleum fuels degrade if they are stored in standard fuel tanks, to some or another extent. But that recommendation from the API is along the same vein of the expiration date on a bottle of milk. Its only worth on the paper or plastic its printed on... And it often benefits the producer of the product not the end user. The API may not be far off on their Cetane recommendation, but that means that the crap that they are refining is just barely meeting the standards. And every engine will respond differently with some running fine on junk and others being much more sensitive.

    Stored poorly it will degrade fast, keep it hot with water, dirt, and corroding tanks well inoculated with biotics -> a problem will develop soon.

    Keep a tank full of dry, clean, diesel well sealed away from the atmosphere by O-Rings that actually seal and a vent that only allows minimal air movement -> you are good for a long ( > 5 years timeframe). Now add any additives that contain alcohols or acetones and this bet is off too.

    I work with diesel’s close brother: Jet Fuels. And since airplanes, and fuel delivery systems do suffer from contamination, like boats do, we introduce a small amount of a very powerful anti-microbial, anti-icing water suspension agent to jet fuels. We are talking a very low concentration of say 0.1% or so. But this stuff is not for the casual user as it will poison you right through your skin’s natural protection barrier. Wear gloves! I add this stuff to the diesel used in my oil burner and garden tractor, and beyond large particals that enter the fuel system, find it noce and clean even after long storage periods.

    What it is:
    Most jet fuel is already compounded with this small amount of Diethylene glycol monomethyl ether (DEGMME or more common: DGME), but not all. So someone came up with the neat idea of sticking nearly 100% in a spray bottle with a calibrated spay rate (High flow bottle -> 50GPM pump, and Low Flow bottle -> 15 gal/min pumping) to spay into the tank as it is being filled up, it all mixes in nicely and you have a good, low concentration mixture.

    The Test:
    I bought a ’80 Oday 30 with a Universal M18 in it. I could get a good look in the tank (plastic) and saw standing water in it. The boat was on the hard for at least 3 years before this, and had bad O-rings on the fuel filler allowing water entry. I calculated out a 2X dose of DGME for a 30 gallon tank and mixed it into a 5 gallon jug of fuel that I pulled off from the boat’s onboard tank. Drained off the standing water and visible goo via a siphon hose and small pump. Dumped in the 5 gal of treated fuel, and let the motion of the ocean at dock complete the mixing after she was slung into the water. After about a day of this slight agitation the dark colored material started to turn a light grey, and then broke down to a fine powdery material.

    Where to get it:
    Since I work in aviation I can grab it off a shelf! Else look at places like ww or you can get some SBG – Sludge Be Gone at a good HIVAC dealer. Look at w one bottle will treat 1000 gallons of fuel.

    Be careful!!! And good sailing.

    Health Hazards
    Acute- Diethylene glycol monomethyl ether (DEGMME), the primary ingredient of Prist Hi-Flash aviation fuel additive, is an eye and mucous membrane irritant, a nephrotoxin and central nervous system depressant. DEGMME can be absorbed through skin in toxic amounts when contact is extensive and prolonged; it is toxic by skin absorption. And it may cause pain and transient injury to eyes. DEGMME may cause irritation to the mucous membranes. Due to the low volatility of this material, it is believed to present no unusual hazards from inhalation when handled at room temperature. The oral toxicity of DEGMME is low. Chronic- Fetal development abnormalities and effects on fertility have been reported to occur from prolonged ingestion by rats, mice and rabbits.

    Chris Patterson likes this.

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