While we are on the subject of fuel does a 144 gal tank actually hold 144 gal?
IIRC, the 144 figure is when the tank is filled to 90% of actual capacity, allowing 10% for expansion due to heat.
But. . .
Be safe - figure 120 gallons useable out of that 144 actual. At 5 mpg, that's 600 miles and it's time to fuel.
(Yes, I'm well aware that many coaches get better than 5 mpg. But I said "Be Safe" - don't push the envelope, unless you happen to enjoy trying to reprime a two-stroke Detroit at Oh Dark Thirty in the rain!)
FWIW. . .