First, thanks to all for your feedback. I did fail to mention that my truck only has a small tank; (approx 27 gal). Also, the gravity-feed RDS diesel tank (which I highly remommend) does not drop diesel into the filler tube as fast as the truck uses diesel. Also, I am trying to cut back on my weight in the truck bed. The door sticker shows that rear axle limit is 6000lbs. With the loaded 5th wheel attached & both fuel tanks full, I am weighing right at this limit; (per CAT scales). So, I will be traveling with only 20-25 gallons in the aux tank. This not only helps with the weight, It also keeps diesel from sloshing out of breather tube on aux tank, this due to the much lower level in tank. And yes, I do take every opportunity to fill up truck after 5w is set up at campsite.