Hi, and Welcome to EM...
You're at an advantage having the Diesel for efficiency, but with prices the way they are per gallon, the savings seems to deminish, I suppose.
Wow, the LB7 series kicks out
520 lb-ft of torque
(and 300 hp)
Do you tow or haul with your rig? That's some serious power, and some respectable economy numbers.
Are you looking for Aero, other mods, or driving style as your means to 25 MPG?
Enjoy the site, and Best FE to Ya
RH77