Prime leasing T700 or T680?

First off Paccar is a gutless pile of poo, if you run heavy and pull mountains, (the real ones out west) you will hate it, pig on fuel too because its working 3 times as hard as a cummins in an identical role/spec.
let me explain:

We have a fleet of T660 Studio sleepers with the 13,000 front axle, higher ply front tires and a full heavy duty moose bumper, if we dip down into the northern states we get random stuff off load boards and its usually heavy, i picked 44081 pounds in waterloo IA, with 5/8's of a tank of fuel (just over half) i was at 79126 (two 150gal tanks) our tire chains are on our trucks 24/7, not that that does much for weight, but i struggle to see how its a problem over 40000 with a 700, unless it mysteriously weighs 5-6000 pounds more than a T660 speced as i mentioned above.

Secondly, I just went from a 2012 t660 with a cummins isx15 @450hp to the Paccar MX thingy.... and fuel economy went from monthly averages of 8.2-8.6 down to so far this month: 6.9 And if i run out of vancouver to calgary fully grossed (87,000) in canada, it would be a 10-11 hour drive, with this paccar motor, i cant make it within the 13 hours of drive time allowed in canada. engine is that gutless.

hope this helps, but why would you want to lease to a crummy big company like that anyways?