Sub Fuel Tanks"To fill or not to fill"

my toyota 80 series handbook says to leave 1/4 of a tank in the sub at least all the time (presumably not neccessarily when you are using it) having said that the sub in my camper is 90-100l and I leave that empty most of the time except on trips

with the Patrol the transfer pump operates for a very short time when you start. I gather that is so the computer can test it is working.

I also try to keep fuel in the sub tank because of this as i dont like the idea of the pump running dry.

I just keep both tanks full and every week just fill up.

If you keep your tanks full you don't have the problem of condensation forming in the tanks. Evan if you have the tank 1/4 full you still have the problem of condensation forming.

Leroy

G Day
as already mentioned leave your tanks full then there is no problem. I had an issue with the underfloor tank in my boat ( 150 lt ) i pulled it out to do some work on the boat and emptied the stainless tank i reacon there was at least 6 lts of water in the tank mind you that took 6 years to build up
Pmacks

I make sure that every seconf tank full or thereabouts I empty the sub tank and when I refill I just fill the sub tank and top up the main tank. That way I know the fuel cannot get "stale" and any water problems ar minmized. I used the same logic on the farm with the tractors/truck/ute and never ran into problems with "stale" fuel.
The only downside is the large lump out of the wallet when you fill up?????????????

In my Troopy I alternate the tanks on a weekly basis.
One week front tank is in use, next week rear tank is in use. Just fill them according to their use that week and run accordingly.
Does two things, I know the oldest any fuel can be is 2 weeks. Also the changeover solenoid for the tanks gets a little bit of excercise each week and hopefully if it's going to fail it'll do it around town, not somewhere between Kickatinalong and Wheelabarraback.
This works well with the Troopy as it has two independant ~90 litre tanks.
Of course, if I'm on a trip they are both full and I pull a little from each alternately. Theory behind this is if I hole one, (Murphy's law says I'll hole the fullest) they both contain about the same amount. I'm trying to make Murphy's decision on which one to hole real hard!

Geoff.

I fill both tanks on my 80 series, run the main tank near empty, switch to the sub and run that down and fill em both and do the same again. Never had any probs with condensation using both tanks frequently. Also gives me longer time between refills.