"Worth it" to top off diesel for the winter?

[mikeeeee]

fill both of them up to the brim.

add quality biocide and a couple bottles chevron injector cleaner.

you'll be good to go when springtime arrives.

a quart of marvel mystery oil wouldn't hurt either.

[topmast]

That air sitting in the top of a partially filled tank over winter isn't the same air all winter. Goes in and out ,like breathing .It may have something to do with temperature change and barometric pressure. I didn't run the numbers in my wet BC air but condensation was very apparent in the day tank sump drain .Killing the water eating bugs addresses most? of the sediment but couldn't help notice old iron tanks eating out at the low point

[valhalla360]

Originally Posted by Cotemar

I have 3 diesel engines, so I try and do the best maintenance I can, so they take care of my family and get them safely home.
.
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Thank you for the emotional appeal. But what does that have to do with the physics of how condensation works?

If you look at the link provided earlier, someone did the math and came up with around a teaspoon of water over the course of a winter. I've done similar calculations and came up with similar results depending on how conservative you want to be with your assumptions.

If you have calculations to the contrary, please share them. Maybe I've made miscalculation or have an incorrect assumption but emotional appeals to not kill the little children don't mean it's correct (sorry pet peeve from my working life where I deal with people trying to go emotional and ignoring factual data.)

Now if we are talking a super yacht with a 10,000gal tank it might be a bit different (though I'm not buying diesel smell comes from corrosion theory).

[valhalla360]

Originally Posted by topmast

That air sitting in the top of a partially filled tank over winter isn't the same air all winter. Goes in and out ,like breathing .It may have something to do with temperature change and barometric pressure. I didn't run the numbers in my wet BC air but condensation was very apparent in the day tank sump drain .Killing the water eating bugs addresses most? of the sediment but couldn't help notice old iron tanks eating out at the low point

Look at the calculations on the link. They take daily air exchange into account.

If it were that simple, a desiccant filter or spring loaded valve arrangement on the vent would be standard equipment to solve the issue.

[hamburking]

I would top off the tanks. So many reasons to do so. Only one reason not to.

I also use diesel from the local land based gas station...have been for 5 years. Never noticed any difference or harm.

I did a lot of research (some of it here on CF) on biocides after I had a bloom in my tank. What I learned is that a few drops of gasoline (per litre) is an excellent and cheap biocide. I wonder how many of those $30 tiny bottles of biocide are actually just gasoline?

I would always top up totally full in the fall. You want to reduce/eliminate the surface area of liquid fuel, thats where condensation takes place. Its also really nice to have a full tank at the beginning of the season...one less thing to worry about. To my 75 litre tank, I would add about half a cup of gasoline each fall, measured by eyeball only. Seemed to work.

[reed1v]

Many decades ago we sailed into Palmyra Lagoon and filled up on diesel fuel that had been sitting in a tank since WW2. Used a baja filter, otherwise the fuel was as good as new. Was the old style waxy diesel. So figure about 30 years in a tropical climate, tons of rain, and the fuel had very little moisture, some crud, and suspect no additives added to it.

Did the same at Dutch Harbor back in the early 70s. Found some jerry cans with what smelled like diesel. Some half empty but all burnt quite well in our old Perkins.

So would not worry about a winter layup. You can always polish the tank as part of your spring commissioning.

[a64pilot]

You will likely never get a manufacturer to recommend an additive unless it's branded by them, reason is they have nothing to gain, and everything to lose.
Why recommend X additive even though you know it works and causes not harm? You gain no profit, manufactures of Y and Z additive will likely squall like stuck pigs, and unknown to you X changes the ingredients and now it doesn't work, and may cause harm, meanwhile your told your customers last year to use it.
Best to tell your customers to use no additive that isn't your brand, and if you offer no additive your stance is use none at all.
You tell them to always top off their tanks, cause it does no harm, and you will have no end of arguments from lots of people who have stories if you don't.

Now I will state that it is my belief that most additives are right up there with fuel line magnets and intake Vornadoes and Teflon oil additives etc., meaning at best they do no harm.

[svthreecheers]

[QUOTE=Teknishn;2255057]I work on larger boats and yachts and I always try to get the owner to keep the tanks topped off for a couple of reasons. First is condensation, the second is the corrosive effects of oxygen on partially filled tanks.

As an example, was working on a 40-meter yacht and the owner and his wife were enjoying cocktails with guests on the 01-level and complained of a diesel smell. Pulled the owner aside and told him that the smell was oxidation occurring inside his fuel tanks which were only about half full and had been for the past month. (Obviously these were not properly lined tanks). The next day we topped off by onloading 12 tons of fuel and voila! Diesel odor gone!

Oxygen in older tanks will cause corrosion which will cause that diesel odor when partially filled. Worse, that corrosion flakes off at some point and then becomes sediment in the bottom of the tank, which then one finds out at the most inopportune moment that the fuel filter is clogged.

Thanks Teknishn
You quoted the best reasons for filling up my fuel tanks for the winter
I have heart so far ( 50 years working in the diesel fuel injection field )
Cheers
Siggi

[Cotemar]

I was hoping the pictures would answer all your common-core-math-problems.

As you can see the condensation is much more than the few drops that your math is showing.

Sometimes real world tells a better story.

Originally Posted by valhalla360

Thank you for the emotional appeal. But what does that have to do with the physics of how condensation works?

If you look at the link provided earlier, someone did the math and came up with around a teaspoon of water over the course of a winter. I've done similar calculations and came up with similar results depending on how conservative you want to be with your assumptions.

If you have calculations to the contrary, please share them. Maybe I've made miscalculation or have an incorrect assumption but emotional appeals to not kill the little children don't mean it's correct (sorry pet peeve from my working life where I deal with people trying to go emotional and ignoring factual data.)

Now if we are talking a super yacht with a 10,000gal tank it might be a bit different (though I'm not buying diesel smell comes from corrosion theory).

[S/V Alchemy]

Originally Posted by doublewide

I went to a diesel engine maintenance conference done by Mack Boring. Several attendees tried unsuccessfully to get the expert to recommend a fuel treatment or additive. Every time someone tried a different tack to solicit advice about additives, the expert said the same thing, "always keep your tanks full to prevent condensation." Nobody could get him to recommend any additive. He repeatedly said, "always keep your tanks full to prevent condensation" or words to that effect. I think he was trying to send us a message.

I have heard the same thing from the chief engineer of container ships dealing with Warsila diesels where the cylinders are two metres across. He said, to paraphrase, "all additives are unnecessary if you keep the tanks free of air by filling them." Implicit in that was his opinion that additives are a waste of money.

For my own part, I filled two 50 gallon black iron keel tanks "up the pipe" in 2008 with ethanol-free diesel for an extended period on the hard during which I re-engined and did other extensive work. Although I did it to keep the tanks from rusting in air, I thought I had nothing to lose to try it in the new engine. So I changed my filters, pulled and cleaned the pickup pipes, noted that there was very little "goo" and gave it a shot.

Worked like a charm. I have 18.5 hours runtime on eight year old diesel. It looks clean and water-free from viewing the filter, and my pressure is nominal. So I think you can either consider the 15 gallons a potential loss due to air in the tank from the vent (maybe) or you can hump diesel in to fill the tanks. Me, I'd fill the tanks, because I want fresh cold diesel in the spring.

[S/V Alchemy]

Originally Posted by Cotemar

My Vote would be to TOP OFF THE DIESEL TANKS.
Condensation is worse in the winter months

This is true, too, because the tank side of the boat can heat up in the winter sun, and then chill at night. This promotes air movement (think a really slow bellows). Air movement is how moist air gets in and out.

[wrwakefield]

OrangeCrush,

We don't put our boat up for winter, but use it year around. [engine, forced air heater, generator, etc.] Therefore keeping tanks full [or empty...] is not an option. [Besides, on most tanks the top has the largest surface area exposed to air, and you would need fuel standing in the fill and vent pipes to keep that submerged...]

Instead we installed the H2Out Air Vent Dryers on both diesel tank vents.

After a year, the desiccant is still dry on both tanks. [it changes from blue to pink when it gets saturated with water...] We are pleased with these results- which are also verified with routine clean samples from the bottom of each tank.

We have a sump drain on each tank for taking samples, and the sight gauge valve is plumbed to the sump drain as well. When we open the bottom sight gauge valve to confirm fuel volume, the inrush of fuel off the bottom of a recently topped-up tank [we let it settle overnight...] into the clear tube gives us a quick visual check without having to drain a small sample.

As an additional safeguard against loose, leaking, or otherwise compromised fuel fill caps, we are preparing to install a ball valve below deck- directly attached to each through-deck fuel fill fitting. That will allow us to treat the fuel fills like we do through-hull fittings; only opening them when needed.

Both tank fills are accessible [after emptying the requisite locker] with a little boat yoga below decks, and since we typically only fuel up 2 or 3 times each year, this seems like a worthwhile trade-off for us. [Not unlike the time needed to use the Baja filter for suspect fuel supplies...]

We do have the ability to recirculate fuel from/to either tank through the twin Racor filters [we can use them individually or in series...] in an attempt at polishing the fuel, and do this regularly as well.

In case this helps sponsor some ideas for your boat...

Cheers! Bill

[valhalla360]

Originally Posted by Cotemar

I was hoping the pictures would answer all your common-core-math-problems.

As you can see the condensation is much more than the few drops that your math is showing.

Sometimes real world tells a better story.

It's hard to tell because it's zoomed in so close but I think your problem is you are putting fuel in the oil fill.

For all we know, you have a leaking head gasket letting a little water in, so it's no evidence it was condensation. (similar issue to people claiming condensation when it's more likely a leaky deck fill)

Also inside a running engine you have exhaust gasses which typically has a much higher percentage of moisture than still air could ever hold. As long as the engine is running, it tends to get flushed out the exhaust system and any trace moisture is boiled out the next time you run the engine (hence one of the key reasons you want to get the engine up to operating temperatures)

On top of that the effect you show may be nothing more than the effect of a couple drops but again, it's a totally different situation from a fuel tank.

Finally, either the math works or there must be another reason. Unless you can show where the math suggesting it's negligible is wrong, there must be another reason you have water in your engine oil.

[a64pilot]

Cotemar,
That is an engine's oil fill tube correct? Water vapor is a product of combustion and is were the moisture in oil comes from, not condensation

[Suijin]

You're going to get proponents of "top them up" and "leave them empty" and the truth of the matter is either route is not going to make that much of a difference if you're going to use the boat next spring and burn through a few tanks of fuel.

One of the best marine diesel mechanics here in Annapolis recommends leaving your tank as empty as possible over the winter. His reasoning is that the amount of condensation that might accumulate is negligible, while the longer fuel sits around in your tank, the more potentially bad fuel you have. He advocates simply avoiding letting fuel sit...filling your tank only as much as you're going to use in a few months, instead of carrying around 100 gallons that takes a year or more to use.

Mainsail, who is fairly well respected in this community, did a test of an empty tank over the winter and found the amount of condensation developed to be negligible as well. That does not mean that he endorses leaving your tank empty. I'm not sure what his specific recommendation is on that.

If you end up with water in your fuel, your primary is going to catch it. If you end up with bugs in your fuel, a biocide and your primary is going to catch it. Choose your poison.