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Old 12-02-2007, 12:22 PM   #1
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Condensation Forming in Diesel Tank

When not RVing, I use my truck only for going to work. Consequently, in the winter, I only put about 400 miles per month on the TV. As a newbie to the world of diesel, I've heard that its best to buy from a station with a big sales volume of diesel since it might be fresher. I've also heard that there can be the problem with condensation forming in the tank (I assume when it is less than half full in the winter).

My questions are:
1. Should I buy small quantities of fuel (e.g. 7-8 gallons at a time) more often in order to always have fresh fuel? With a tank below half full, will this cause condensation? or
2. In the winter, should I keep the tank between 3/4 full as a minimum?

Would prefer avoiding the inconvenience and expense of using fuel additives. Appreciate opinions on this topic.

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Old 12-02-2007, 01:05 PM   #2
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Hello B&J -- Are you in San Francisco? I'm not sure you're going to see the freezing conditions I've always associated with tank moisture problems. Before the days of gasohol we got used to dealing with condensation on the inside walls of gas tanks. Empty tanks leave more side walls for condensation. That part of the answer always was -- have more fuel in the tank to lessen condensation. I'll want more experienced diesel owners to comment about additives.

We've got a Subaru Outback and my 3/4 ton GMC D/A. I get 20+ mpg with mixed 55mph highway driving. The Subaru only does a little better. We tend to take the truck when traveling any distance to keep the tank turning over.

This link doesn't discuss your problem specifically -

I'd probably head over to Diesel Place - Duramax Diesel Discussion Forums and do some browsing. Ask them -- but if you join, remember, you started here first! Come back, y'hear?


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Old 12-02-2007, 01:44 PM   #3
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Ask any farmer.....if you want to avoid condensation in the diesel fuel tank (trucks, tractors, equipment) always fill the tank when stopping for the day. That water will play the devil with injectors and the pump. $$$$$$$.
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Old 12-02-2007, 02:19 PM   #4
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Diesel fuel and condensation


You are correct to be concerned about moisture in the fuel tank. It is best to always keep the tank full to prevent this. The water that gets in the fuel is usually a result of moisture in the air. By displacing the the air with fuel this problem is eliminated. Another problem commonly seen in jet aircraft is the growth of microbes in jet fuel/diesel. You can do a google search to find more information about this. I currently drive a silverado 3500 duramax and have had no problems. However, I have had known several people who have had the fuel filter clog causing a loss of power.
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Old 12-02-2007, 02:28 PM   #5
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To help reduce moisture and microbes, aka slime, keep the tank full, and use a good fuel treatment, such as Biobor's Diesel Doctor.
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Old 12-02-2007, 02:43 PM   #6
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hi b/j....

inconvenience and cost?

a good diesel fuel additive is hardly either.

keep the tank full and add 2 bucks of stanadyne...

Stanadyne Corporation - Home Of High Quality Diesel Fuel System Components

even once a month this would be a quick easy step when the truck isn't getting driven much.

otoh the modern fuel/water separators work great but it would be a bigger pia and more costly...

to drain the separator and change fuel filters more frequently than the scheduled interval...

so take your choice on which approach is easier and less money.

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Old 12-02-2007, 05:39 PM   #7
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It was 12 degrees when I went out to get the paper this AM....I use Biobor Diesel Doctor and keep the tank full on my Kaboda tractor. Biobor is also excellent for keeping microbes from growing in your tank as in a twin engine diesel trawler.
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Old 12-02-2007, 06:32 PM   #8
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For thos gassers out there. If your TV or RV sit for extended periods Sta-Bil works wonders to keep your fuel fresh. I've used it for years in my boats.

What is the best additive for Diesel fuel, not just for water but for stale diesel?

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Old 12-02-2007, 06:35 PM   #9
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Originally Posted by rmpray
For thos gassers out there. If your TV or RV sit for extended periods Sta-Bil works wonders to keep your fuel fresh. I've used it for years in my boats.

What is the best additive for Diesel fuel, not just for water but for stale diesel?

Don't forget to treat your generator too, if it's a gasser...


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Old 12-02-2007, 06:46 PM   #10
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Back when I was using additivies I used Stanadyne. I've found I get the same results mixing in bio-diesel (actually I think it works better) with petro diesel. That won't work for you folks in climates were freezing may occur as bio could gel (unless you mix petrol deisel in at 50% or better). Best bet is to keep the tank topped off. With the generator I try to run it at least once a month and keep fresh gas in it. But because that uses so little fuel I use a blend of Sta-Bil and Techron in the gas can.
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Old 12-02-2007, 06:51 PM   #11
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Your 2008 Duramax comes with a very good fuel/water separator, drain it each oil change or more. Most manufactures recogmmend to use additives ONLY WHEN you get bad fuel and when the temperature drops to the point where the fuel will gel. Get your fuel from stations that service their filters often, ask them.
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Old 12-07-2007, 06:28 AM   #12
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In the winter (if its cold as it is here in the midwest) treat a 1/2 tank like an empty tank and fillerup. Every oil change gets a fuel filter in the winter.
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Old 12-07-2007, 07:00 AM   #13
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Diesel Tank

I know more about JP (jet fuel) than Diesel.
The Capacitive Fuel Probes in certain NAVY aircraft have teflon standoffs to seperate the two fuel quantity measurement components.
The JP of the time and present asorbs so much moisture that it promotes the growth of algae on the standoffs which shorts the probes and makes them useless.
NAVY petroleum chemists have written books on the subject and how to minimise the problem, but few actually read these manuals because they already know it all.
There are probally additives out there that minimise the effects of this asorbed moisture (bourne) and the unbourne moisture (the stuff you can see rolling around in the corner of the tank).
Fuel Injection Pumps and injectors are very precision devices and are easily damaged by even a drop of moisture setting in the "critical spot" (reference the GM diesels of the early 80s and those roosa master injection pumps).
1. Keep the tank full. Gas tanks are now sealed to a certain extent and keep the temperature changing breathing of the tank to a minimum. I assume diesel tank are the same, given the EPA's exuberance.
2. Use a good additive. Most of the farmers I have spoken to in the western part of the State of Virginia use Essentulube products and have for decades. Its not cheap, but is is far cheaper than repairs and the inconvinence of (diesel) equipment that dosen't work properly after weeks of setting idle. They usually bought the stuff in 55 gallon drums.
3. Listen to the experienced mechanics (politically correct enough?) on the forum for tips. They have seen the common and weird problems because they have been on the "front lines" for years and decades.
I personally don't own a diesel because I don't use a power plant "severe" enought to deep a diesel running properly.
Just my two cents worth.
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Old 12-07-2007, 11:34 AM   #14
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It gets pretty cold here in RI...even colder up North in NH where we ski a lot. One long weekend up there last winter, temps were -25 F each night. I thought I best use the block heater for the first time, so I fished around and finally found the cord, plugged it in at night. Well we were heading home on Tue, I get a trouble code, truck goes into "limp home" mode. I knew there was a dealer up the road. They were great, brought us right in and helped us out. They told me the code was for using the block heater when it wasn't cold enough! -25 F!!!
This is my first diesel, so I was curious and quizzed them some more. Remember, some of these Northwoods guys (mechanics) are pretty grizzly kind of guys, you know; chop wood, shoot deer, drive big *ss diesel trucks and skidders (loggers) in VERY COLD weather...know what they said; the additives are put in seasonaly by the refiners, they NEVER put anything in the tank, and they NEVER use block heaters (they did with older diesel engines) but not with common rail injection. They said the glo-plugs run so hot now, you don't need it.
Well, I never put anything else in my tank after that, tucked that blocker heater cord away, and just try to keep the tank relatively full.
Like you, we use our truck pretty much for tow duty, or other adventures. But it sits a lot (not used for commuting).
Change your filters when the DIC says so, buy your fuel at the most popular place around, and keep it full. You'll be fine...


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