Leave a Diesel tank empty or Fill it

[GreenWave]

Hi,


I have three diesel tanks on my Catalina. One is empty now and I am thinking I may leave it empty for rest of the summer as I won't need it. The other two tanks will be kept reasonably full and used regularly.


Thoughts on this idea? Or should I fill it partially knowing the fuel will sit for several months perhaps.

[slug]

Originally Posted by GreenWave

Hi,


I have three diesel tanks on my Catalina. One is empty now and I am thinking I may leave it empty for rest of the summer as I won't need it. The other two tanks will be kept reasonably full and used regularly.


Thoughts on this idea? Or should I fill it partially knowing the fuel will sit for several months perhaps.

When possible I leave them absolutely empty ... perhaps 5 percent

This makes cleaning the tank during the off season much easier and keeps biological growth off the tank walls

I have never removed any water from the tank

[a64pilot]

Why not fill them all, add a fuel stabilizer and use them all?
If I were to empty one, I’d want it as completely empty as possible and I’d likely add a desiccant filter on the vent line, the desiccant filter will of course absorb any moisture but also most likely any spores that may get in that way.

[GreenWave]

Originally Posted by a64pilot

Why not fill them all, add a fuel stabilizer and use them all?
If I were to empty one, I’d want it as completely empty as possible and I’d likely add a desiccant filter on the vent line, the desiccant filter will of course absorb any moisture but also most likely any spores that may get in that way.

Dessicant- interesting idea. Any source on what works for a vent line? Are they purpose made? The empty tank is as dry asit will get without opening it up - ran until engine sputtered.


Main reason I don't want to use them all is the PITA to fill three different tanks - I know, not the best excuse!

[slug]

Originally Posted by a64pilot

Why not fill them all, add a fuel stabilizer and use them all?
If I were to empty one, I’d want it as completely empty as possible and I’d likely add a desiccant filter on the vent line, the desiccant filter will of course absorb any moisture but also most likely any spores that may get in that way.

On big yachts the main fuel. vent line has a valve and can be shut off to avoid humidity and fuel contamination

Also possible to use this system on small craft

[zemurray]

Personally I try to keep it full. I use a biocide treatment. I don’t like the idea of condensation in the tank. General practice on anything with a motor was to always store with a full tank. Probably not as big of a deal on a diesel, but with gasoline empty tanks corrode and cause all kinds of issues. diesel is stable in a tank for a long time.

[kmacdonald]

Read this: https://pbase.com/mainecruising/fuel_tankt_condensation

Leave it empty. Less weight.

[GarthGregory]

Always Always keep it full - That way you limit the airspace and keep the keep condensation to the minimum and thereby minimize water in the fuel - otherwise you promote the growth of Algae .Use a fuel biocide to help stabilize the diesel .

[a64pilot]

Originally Posted by slug

On big yachts the main fuel. vent line has a valve and can be shut off to avoid humidity and fuel contamination

Also possible to use this system on small craft

What keeps it from building pressure or a vacuum?

[a64pilot]

Originally Posted by GreenWave

Dessicant- interesting idea. Any source on what works for a vent line? Are they purpose made? The empty tank is as dry asit will get without opening it up - ran until engine sputtered.


Main reason I don't want to use them all is the PITA to fill three different tanks - I know, not the best excuse!

There are many, good ones you can remove the desiccant when it turn pink and dry it out in the oven and replace it. They will absorb all moisture before it gets into the tank
https://diesel-fuels.com/desiccant-f...ent-breathers/
I had a desiccant filter on my underground and above ground fuel tanks on the farm, the underground really didn’t need one as much as it’s temp should be stable, but it didn’t hurt.

I put my little airplane in storage, one of the things I did was remove the spark plugs, and install desiccant filled spark plugs.
Really a lot ways / uses to store items using a desiccant
https://www.aircraftspruce.com/catal...ickkey=3020435

[Cheechako]

I'm on the fence on this. Moisture collects inside a tank. If the tank is steel I would fill it. If plastic or aluminum I may not.
The thing about diesel treatment is it only works temporarily. I've had heavily biocide treated diesel that has sat around start to look like a swamp with things growing in it. So bad you can't see through it in a jar.

[KP44]

Originally Posted by slug

On big yachts the main fuel. vent line has a valve and can be shut off to avoid humidity and fuel contamination

Also possible to use this system on small craft

I installed a shut off in my vent lines. Not difficult when I replaced all the tanks. I always shut them off when we leave the boat. Hopefully it cuts down on condensation.

[Glacier Crews]

For a number of reasons, only one may be relevant, we left 200 gal of diesel in our 3rd tank. Five years went by. No treatment, just fuel. Tank full. In year six we finally drained that tank to polish and dispose of fuel, only to discover that the fuel was in perfect condition as was the tank. So we polished it in our onboard West Coast fuel polisher and used it. Used it in 2019 put into tank in 2013 or 14.

Shared information.

I like to remind people that advice Is probably “worth what you paid for it.”

[fred4936]

I always wondered about this myself. Last fall I drained the tank and cleaned it. I left it closed and empty. A week or so ago I took the panels back off to give it a once over. It was dry inside. So I gave it another wipe down with kerosene and buttoned it up. Not sure I will do this every year, but I do like knowing that at least right now the tank and system are clean.

[Maka]

All 4 25 gal. steel tanks always topped off FULL.
Preserves the tanks from rust. Reduces water in the fuel.

My Perkins burns 1 gph. Two 60 gph. racor filters, filter fuel on the way to the engine.

My filter system polishes all fuel being returned to the tank.