Fuel questions....

I hopefully will be in the situation where I need to buy some diesel fuel. I have been buying diesel fuel for many years, but only buy about 30 gals at at time on average. With a 40 gal tank, I don't go through much fuel and it sits around a long time. I have always used a fuel stabilizer/biocide.

Now I am looking at buying fuel (and burning fuel) in much larger quantities and could use some advice. I have read through all the threads that I can find here and boatdiesel.com but am still a bit confused.

Questions:
1. Is it "better" to fill up the tanks and keep them topped off, or is it better to only take on the fuel that would be used in a reasonable amount of time?
2. What is "reasonable" in #1?
3. Is using a fuel stabilizer/biocide reasonalbe?

Opinions welcome.

OK. I lost what I had written, so now you get the short version.

All of the above. Pretty much whatever you do or don't do, will make very little difference.

Yes, i would always keep the tank topped up. But beyond that,,, I have read so much stuff, much of it contradictory, that the only reasonable conclusion is it really does not make much difference.
!
Now, I will give you some advice for a long and happy life: Only believe in 10% of what you hear or read and 50% of what you see.!

Fill-up when convenient but full is better

We try to keep the tanks as full as possible but don't go out of the way to do so except at the end of the season. Always winter store 7/8+ full.

If we're on a long cruise we'll fill up when convenient and the price is right. While underway cruising we often run the tanks down to 1/3 or less before filling. When she's in the slip tanks are usually never less than 5/8 full for any period of time.

Depending...condensation in boat tanks is more myth than truth.


See Compass marine demonstration and explanation if you don't believe just me.


Diesel lasts a long time...but some chemistry and some biology can happen. Biology much faster than chemistry...months versus years.


I recommend just buying and storing what you think you will burn over say 3-6 months and don't worry about it.


If longer and your portion of the country suggests biocide...use it.


Other than that...if you keep burning off the fuel...there is little to contaminate.

dhays said:

I hopefully will be in the situation where I need to buy some diesel fuel. I have been buying diesel fuel for many years, but only buy about 30 gals at at time on average. With a 40 gal tank, I don't go through much fuel and it sits around a long time. I have always used a fuel stabilizer/biocide.

Now I am looking at buying fuel (and burning fuel) in much larger quantities and could use some advice. I have read through all the threads that I can find here and boatdiesel.com but am still a bit confused.

Questions:
1. Is it "better" to fill up the tanks and keep them topped off, or is it better to only take on the fuel that would be used in a reasonable amount of time?
2. What is "reasonable" in #1?
3. Is using a fuel stabilizer/biocide reasonalbe?

Opinions welcome.

Click to expand...

No doubt there's a lot of snake oil on the market where fuel additives are concerned. I believe you could bottle diesel fuel or kero, add some dye and make claims about smoke, fuel economy and algae and it would sell. And for the record, algae is virtually never present in diesel fuel, as a plant, it needs sunlight to carry out photosynthesis, of which there is precious little in the average fuel tank.

Having said all that, there are additives whose claims are reasonable, and they do work as advertised in my experience. In all the years I ran a boat yard, in which hundreds of boats were winterized, I used StaBil for diesel and gasoline stabilization, I'm firmly convinced it works. Diesel fuel is pretty inherently stable, at least for 6 months to a year (although ULSD has reportedly reduced this somewhat). After that a stabilizer like StaBil makes sense, although you should not stabilize old fuel, i.e. don't add it after 6 mos.

If, however, water is present in the tank all bets are off, as it will support biological life (which is typically bacteria and mold based), which can wreak havoc on tanks and fuel systems. Biocides will kill these organisms, but it's a crap shoot as you can't be sure how much to use, and the organisms, being animal based, actually have skeletons, which accumulate at the bottom of the tank after they die, and those skeletons are abrasive. The byproduct produced by these organisms, hydrogen sulfide, is acidic and corrosive to metallic tanks and fuel systems. You get the point, water in fuel tanks is undesirable in so many ways. Removing the water, therefore, using a stripper tube or drain, is far more preferable than treating biological growth by which it is supported.

The other major issue that can affect diesel fuel is lubricity. Lubricity is an article unto itself, however, in short, even diesel fuel that meets ULSD S15 requirements (contrary to popular belief and many articles that have been written about it, the ASTM diesel fuel standard, D975, remarkably, does not include an adopted lubricity requirement, I've read the standard), doesn't meet the requirements of many diesel engine manufacturers. Therefore, using an additive such as Stanadyne Performance Formula All Season, which includes a lubricity additive Performance Formula « Stanadyne Additives(they do offer a stand alone lubricity improver, as well), while not mandatory, is very good insurance. No connection with the company, (or StaBil), I just use it, and recommend it, with every fill up and have for years. Stanadyne is made by a company that manufacturers fuel injection systems, which, in my estimation, makes them trusted enough to formulate and offer a product of this sort.

Stanadyne and StaBil include a demulsifier, which encourages water separation from fuel, enabling it to be drained off or sucked out of a tank, while many other additives include emulsifiers, just the opposite, which encourage water to mix with fuel. If you have a water seperating fuel filter (or fuel tank water drain). It strikes me as counterproductive to attempt to force water to mix with fuel, and have it pass through filters and into injection systems. And again, not knowing how much water is present makes using an emulsifier a gamble at best.

Just my opinion. With the exception of anchors perhaps, few subjects are as contentious and strewn with opinions as fuel additives, and with good reason, so little is, or can truly be known about them without lab testing.

Depends if you are running the boat or if the boat is sitting in place for many months at a time. If you are running the boat, do whatever you want and save your additive money to buy more diesel fuel. I remember when fuel prices were so volatile in 2007-2009. When prices were going up rapidly we topped off at virtually every dock stop. When they were plummeting we'd wait until we got to the next cheap commercial dock or place where we could call a truck, sometimes down to as little as 10% or less of capacity. In our experience additives are a waste of money unless you are putting the boat into exposed storage for a long time, and even then somewhat questionable.

What psneeld said but first you need to know that most diesels pump a lot of fuel and return most of it to the tank unless at full load. This cools and lubes the injector system and also runs lots of fuel through the filters.


Personally I only filled the tanks when I planned a lot of use. Other times I tried to only have as much fuel on board as needed the theory being that the less fuel in the tank the more frequently it would be filtered, see above. The mixing problem if you have a math background. Also less fuel means more sloshing to stir up junk when it gets bumpy. Anyway that worked for me in hot steamy Florida for 17 years.


I also never used any additives. Just clean source fuel.

What we do:
100 % filling end of season to avoid condensation over winter, since we don't move out of the slip for 3 month. Over the season we fill up if we need to and fuel at reasonable price available. We did never run the tanks down below 10%.
Honestly: no clue whether this is smart or not. But it worked so far ...


best regards / med venlig hilsen
wadden

Greetings,
Mr. b. "...that most diesels pump a lot of fuel and return most of it to the tank..." With Ford Lehman's being one exception.

RT Firefly said:

Greetings,
Mr. b. "...that most diesels pump a lot of fuel and return most of it to the tank..." With Ford Lehman's being one exception.

Click to expand...

The Rodney Dangerfield of diesels...they get no respect....

May have to nickname mine Rodney....

dhays said:

Questions:
1. Is it "better" to fill up the tanks and keep them topped off, or is it better to only take on the fuel that would be used in a reasonable amount of time?
2. What is "reasonable" in #1?
3. Is using a fuel stabilizer/biocide reasonalbe?

Opinions welcome.

Click to expand...

I think the answer to all the above is "it depends." As to #1 and #2, much depends on how long you're talking about the fuel being stored and definitely of "reasonable." As others have pointed out there's the issue of fuel contamination and the one of degradation. We keep near full, but then we run through the fuel quickly. If it took us three years to use our fuel supply then we'd keep less.

As to #3, we determine based on the fuel we're getting. Valvtech has an additive in it. So do some other brands. However, elsewhere or when uncertain, we toss in an additive, especially when out of the country. When traveling in areas of uncertainty, we test the fuel before filling. However, you can only get immediate readings on water and visual clarity and on degradation. Any microbial test requires time to develop.

Is it worthwhile? Well, in three years and over 50,000 nm we've only found two problems of water or degradation. (One of them also turned out to have a microbial issue). However, those two times could have been real issues. One was water that could easily be seen. That's a simple thing to check and I'd recommend it especially in low volume marinas or those just resuming business at the start of the season. We actually found the one issue of degradation (through detecting high levels of acidity) in a situation that really surprised us as it was a fuel truck delivery (out of the country). The driver stated that they didn't sell much and hadn't had a delivery to them in quite a while, maybe two or three years.

I wish I'd known about testing when we lived on the lake. Every spring, dozens of boaters would have issues from water in their fuel. At least one marina on the lake would have issues.

I would be wary of the Valvetech claims and any other additive added at the marina level.


A certain manager I know hadn't added the additive in years despite advertising it.


Like many diesel options, whether the red dye or advertised additive...it is added at the truck or tank fill and even ethanol is often shorted when analyzed in a lab.


All over? Every marina? heck, I can't answer that...but in my little world...there's a lot amiss compared to what people think is reality.

psneeld said:

All over? Every marina? heck, I can't answer that...but in my little world...there's a lot amiss compared to what people think is reality.

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I don't know what people think is reality or how much is amiss. The only thing I do know is that it's quite possible to get poor quality diesel. I know on low sulfur vs. ultra low sulfur you could possibly not get what you're buying. Where I've got equal concern is on other lubricants. When you buy 5 gallon pails or 55 gallon drums of oil, is it always what you thought you were buying? The reality is you just buy from someone you believe to be trustworthy as much as possible and have your lubricants tested. It may not be an engine issue, but could be what was delivered.

Still, I see no reason for paranoia. Just awareness. We take extra precautions based on some of the places we go.

I would trust a 5 gallon pail or 55 gallon drum of oil from a manufacturer, who knows well that their oil might be tested as opposed to a local marina that depends on a truck driver or marina worker to pour in an aftermarket additive.

Paranoid not at all... just have a hard time with something that I can't trust and have to decide whether to supplement or not.

It is just a shame as getting fuel tested seems crazy when so much of the time you are going to start using it immediately.

I might consider it for a big tank load and a long voyage. Just as I would let it settle and polish it in some fashion.

Wxx3 experienced it first hand on his voyage.

Dave, asking about diesel additives on TF falls somewhere between "courageous" and "character forming", using the open ended sphincter scale.
An important consideration is where you get your fuel. You want a good safe source, a load of bad fuel or fuel with water is a PITA. Ask around. Look for somewhere that has a good reputation, perhaps a supplier that does high volume high turnover sales, including to commercial ferry type operators.
A diesel mechanic told me to take a glass container and squirt some fuel into it before filling tanks. If you see "bubbles" and they remain, they are water, not air bubbles, beware.

psneeld said:

I might consider it for a big tank load and a long voyage. Just as I would let it settle and polish it in some fashion.

Wxx3 experienced it first hand on his voyage.

Click to expand...

We do long voyages and big tanks and that is the primary reason we test. Also, the primary reason we have polishing.

RT Firefly said:

Greetings,
Mr. b. "...that most diesels pump a lot of fuel and return most of it to the tank..." With Ford Lehman's being one exception.

Click to expand...

Don't mean to derail the thread, but I'm curious. Do Ford Lehmans not return diesel to the tank?

Graycenphil said:

Don't mean to derail the thread, but I'm curious. Do Ford Lehmans not return diesel to the tank?

Click to expand...

Virtually none....

I have never heard a concrete answer...

Anecdotally, during an engine run at a class in a parking lot, I heard that the instructor never hooked up a return line while running it, I also couldn't get any at 1000 RPMs in 5 minutes when testing for my new fuel manifolds.

Thanks Psneeld. Interesting, so it has a return line, but doesn't return much fuel. Somehow, the lift pump delivers just the amount of fuel that the injection pump uses?

Wxx3 said:

I have read so much stuff, much of it contradictory, that the only reasonable conclusion is it really does not make much difference.
!

Click to expand...

This is also my experience. My reasoning, which explains my success in having burning a good amount of oftentimes 1+ year old fuel (I hold 2300 gallons and don't always burn it all in a year), is that with really good filtration, nothing bad (ie, water, growth or other particulates) can get through, so the only other downside to old fuel is a loss of cetane. Although I only occasionally run my engines anywhere near max hp or 90% load anywhere along the curve, I have never had combustion problems with old diesel -- no lack of power, no smoke and no temp problems.

Thank you all for taking the time to respond. I honestly really appreciate it. I will have many similar questions in the future and I know there isn't necessarily any "right" answer.

If the sale goes through, I think I will try and fill up the fuel when I see a good price. I will also use a fuel stabilizer/biocide as I have been used to. I am tempted to change all the fuel filters even though there is not current vacuum issues, but at least I will then know when and with what the filters were changed last.

Dave,

I am in the same situation as you. We have a Cat 36 that we keep full of fuel, easy to do. I always use an additive because I buy fuel in April and fill in October when we get back from our annual trip north.
Last year we bought a powerboat to supplement our travels. We are going through a lot of fuel, so I am not bothering with the additive. You are south of Seattle, I believe, so your best bet would seem to be Des Moines for fuel. Their prices are always lower than saltwater sites in Seattle. Don't overthink things, just enjoy the experience.
Good luck with your survey.

Thanks. I saw that Des Moines has pretty good prices and are pretty close to Gig Harbor. Survey was good, waiting on the oil analysis. If nothing horrible shows up, the deal should close in a week.

When that happens, maybe I can get the time to cruise into Hoods Canal, something I have never done in all my years of sailing around the Sound.

Actually today Oak Harbor is at $1.52, Brownsville at $1.75, Poulsbo at $1.75, Port Orchard at $1.75. Des Moines was at $1.84 on March 1. I don't know their current price. It's all a moving target so always best to check current prices.

Yup, definitely a moving target. Oak Harbor always seems to have very low fuel prices, but is in the wrong direction. Des Moines currently lists $1.57 on their website and is kind-of on the way. If I could figure out how to update the fuel price on Active Captain, I would. Of course, who knows what it will be like in another week.

BandB said:

Actually today Oak Harbor is at $1.52, Brownsville at $1.75, Poulsbo at $1.75, Port Orchard at $1.75. Des Moines was at $1.84 on March 1. I don't know their current price. It's all a moving target so always best to check current prices.

Click to expand...

You must be lucky guys over there. Expect you are talking $ / gal?
I'm paying that as € / liter ...


best regards / med venlig hilsen
Wadden

dhays said:

Yup, definitely a moving target. Oak Harbor always seems to have very low fuel prices, but is in the wrong direction. Des Moines currently lists $1.57 on their website and is kind-of on the way. If I could figure out how to update the fuel price on Active Captain, I would. Of course, who knows what it will be like in another week.

Click to expand...

Well, I'd make sure their website is up to date. Don't know which is most current.

Some folks don't believe that condensation in a partially empty fuel tank is possible while others have seen the results of it. It probably has something to do with the part of the world you live in and keep your boat in. Air moves in and out of the tank as fuel expands and contracts with temperature change and if the air is humid, it can definitely condense on cold tank walls or fuel.


Many "experts" recommend keeping the fuel tank as full as possible to avoid this possibility. As I recall, this is recommended in my boat's owners manual.

BandB said:

Actually today Oak Harbor is at $1.52, Brownsville at $1.75, Poulsbo at $1.75, Port Orchard at $1.75. Des Moines was at $1.84 on March 1.

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.I wish.

BruceK said:

.I wish.

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We paid $1.78 in Fort Lauderdale today. Actually $1.68 after volume discount.