Auxiliary tank - full or empty?

If the tank is full there is less room for condensation to form. I always fill both tanks before I put the Cummins away for the winter.

My thought is keeping full. Avoid any moisture or condensation in the tank.
Weight and cost are negligible factors for me.

My aux tank stays full all the time. My truck is rarely used in the winter. Never had a problem with the fuel, and I don't use any additives.

I keep mine full at all times, trucks filled from the tank and tanks gets filled at the pump, keeps the diesel fresh. I use the TSD fuel card currently at the T/A truck stop for best price. Closest is 75 miles from home in a city I get to once a week or maybe two at the most.

It won't hurt to let it just sit full, but why...
Either leave it empty or empty-ish, or continue to use it if it's a gravity feed tank. Is it an actual auxillary tank, or a slip tank you have to pump in?

Unless the truck is just parked, then I'd leave it empty.
If it's parked outdoors, condensation is a concern. In doors, not hardly at all.

I'm not concerned with the weight or cost of the extra fuel. Do I have to put an anti-algae agent in the fuel if I let it sit for 6 months? If so, recommendation. The weather will be cool and humid (rain).

Fill it up , helps prevent condensation , also fuel is pretty cheap now .

jdc1 wrote:
Diesel? Diesel will last a day before forever. Gas? Gotta keep cycling it.

This. But you also need to think about the extra fuel and wear needed for hauling the weight of fuel you don't need.

Diesel? Diesel will last a day before forever. Gas? Gotta keep cycling it.