I usually start looking when I get down to a 1/4 of a tank of fuel.
We do frequent truck stops as they are typically easier to get in and out of and when using the truck lanes, those pumps are FAST !!!!
The truck stops are usually faster during the summer or holiday season with a lot of drivers on the road clogging up the auto lanes and blocking the Diesel pump while they take the kids to the bathroom.
Have thought about adding an Aux Tank for more capacity (our factory tank is 36 Gal), but hard to justify the expense as it is usually no big deal to stop and get fuel, use the bathroom, let the puppy dog Pee Pee and get something to drink every 250 to 300 miles.
Robert & Bale the "Traveling Dog"
2012 GMC 3500HD DRW