To fill or not to fill....(the diesel tanks)

[mwardmoeller]

Hey, All.

I'm sailing a Westsail (Wetsnail) 32 with 2x40gal=80gal of fuel and a brand new Beta 38 which consumes well under .8gal/hr

Fortunately I'm cruising the Caribbean this winter after departing Chesapeake in Oct. Since then, I've only burned about 40gal of diesel from the tanks (I like to sail, hate motoring, and get 90%+ of my power from solar.) That means my tanks are about 1/2 full. As I'm spending the summer in/near Grenada, I certainly don't see my fuel being used anytime soon. I am currently in Sint Maarten so can top up the tanks with reasonably fresh/quality fuel. But.....
1. is it better to continue burning the fuel in the tanks to just use it.
Obviously, that leaves more air space and room for condensation etc.
When the tanks get lower I will fill up or...
2. Is it better to keep the tanks full which minimizes air space but allows
the fuel to get even older given my burn rate.

I can see advantages/disadvantages to each. I use Star-Tron stabilizer whenever I fuel but, again, that's very infrequent. Guess it's a good "problem" to have. Thoughts/opinions welcome. Thanks

[Rucksta]

You can never have too much fuel.
Unless you are on fire

[NYSail]

I like to use all fuel before filling to keep things fresh, however if I was cruising as you are just my opinion but I would fill up…. Never know what may be around the next corner.

Greg

[JBP]

You could put in a fuel polisher (basically an extra pump and filter) to keep your fuel clean. With a couple extra valves, it could also serve to pump from one tank to the other if needed.

[Bobby Lex]

For long term storage the rule of thumb as I have always understood it is to keep the tank(s) topped off because of the condensation issue. Use a good fuel treatment additive as well.

Practical Sailor has a good article on additives. https://www.practical-sailor.com/boa...esel-additives

Bob

[Rucksta]

You could burn tank one, switch to tank two and look for a fill for tank one.

On the full unused tank close the breather.
Modify the return line so that fuel is returned to the tank in use.

These changes will extend the shelf life .

If the fuel and water tanks are arranged port & starboard use opposed fuel & water to maintain balance.

I keep a 20lt gerry can as emergency fuel.
At the fuel wharf I siphon it into a tank and refill from the bowser.
The contents are checked before filling the main tank.

Hope this gives you some options other than full or empty

[S/V Illusion]

Condensation in a partially full tank can occur but is generally more a myth than a real problem. What is a real problem is degradation of diesel fuel. Diesel can get “old” and it doesn’t age well.

If you want to avoid fuel problems, the goal should always be to burn fresh fuel whenever practicable.

[BlueH2Obound]

If out cruising, my preference is, if you have access to reasonably cost, quality fuel, fill the tanks. You never know when you may need it!

2nd the suggestion to use the appropriate fuel stabilizer/biocide when you fill up.
My Dad told me years and years ago, "The fuel on the ground is of no use to you!"
To paraphrase for boats, "The fuel in still at the last harbor is of no use to you!"

The rest of his advice was:

"Three things that are of no use to the aviator

• The runway behind you
• The altitude above you
• The fuel on the ground

Enjoy!

[Kd9truck]

Originally Posted by S/V Illusion

Condensation in a partially full tank can occur but is generally more a myth than a real problem. What is a real problem is degradation of diesel fuel. Diesel can get “old” and it doesn’t age well.

If you want to avoid fuel problems, the goal should always be to burn fresh fuel whenever practicable.

I second this, stale diesel fuel gets a varnish quality to it, it will grip to metal and gunk up everything while still passing thru the filters. It’s really more of s a “new problem” because EPA regulations have taken stabilizers and biocides out of the fuel making it more perishable.

[SVTatia]

When I bought my boat the tank was full and the fuel was 7 years old when I launched after the refit. I have had no issues whatsoever.

My only advice is if you are in a place that sells good quality diesel and has a busy fuel dock, take advantage and continue to use biocide.

[NorthCoastJoe]

I would run one tank at a time if it's going to be a long time between fills and you don't need the fuel. I would also clean the empty tank and seal it until you need it.

[Lee Jerry]

My recommendation is to fill* both tanks, using appropriate additive, and then to draw from one tank until empty**, then switch to other tank. Re-fill first tank when needed and/or at the next convenient quality source. Draw down second tank until empty** and repeat. At your current rough usage of 40 gal in 6 months, you'd go through each tank within a year. This should be fine in terms of age. (Obviously top off both if going for longer trip.)


* Maybe short the tank a little since your usage is relatively low, so only fill to 80-90%.


** Generally prefer not to run the tank "dry," avoiding having to bleed the engine, so maybe stop at 10-15% capacity, depending on shape of tank. Also reduces picking up the crude from the bottom.

[thinwater]

Using up fuel is always best.


You could (I would) install a silica gel vent filter. It will eliminate condensation/absorption and will greatly reduce air exchange (oxygen).
https://h2out.com/fuel-guard-avd-2/
Yes, I used them, tested other types, and put several into trial with friends in Washington State etc.


Installation requires some thought. You need to keep fuel overfills out (Parker Lifeguard) and water out (high loop).



Obviously no interest. I test stuff and I have used similar stuff in industry.


The gel can be regenerated in a pan after 2-3 years, as needed. Easy.


But the end result is VERY dry fuel.

[stormalong]

Originally Posted by Rucksta

You could burn tank one, switch to tank two and look for a fill for tank one.

On the full unused tank close the breather.
Modify the return line so that fuel is returned to the tank in use.

These changes will extend the shelf life .

If the fuel and water tanks are arranged port & starboard use opposed fuel & water to maintain balance.

I keep a 20lt gerry can as emergency fuel.
At the fuel wharf I siphon it into a tank and refill from the bowser.
The contents are checked before filling the main tank.

Hope this gives you some options other than full or empty

NEVER EVER close the breather of a fuel tank full or empty. Thermal expansion and contraction will cause partial pressurization/vacuum of the tank stressing the tank and every fitting and hose. Fuel tanks are not made to be pressurized. An extreme temperature change and you may end up with a bilge full of diesel.

[Chris Cringle]

Fill it. Aged diesel is not a problem. Water in the tanks is.