EZ Dodge Cummins Questions

my 95 4x4 auto with Cummins gets 19 mpg driving 25 miles to & from work Set cruise at 60 mph

Mine as some exhaust work, timing up to 16 deg and pump tweeked. Yeah is lays down some smoke, but sure runs good. I did it for pulling not a race truck.

pulling my 24' enclosed car hauler at 75 to 80 mph gets 11 to 12 mpg, pulling 12' enclosed trailer 13 to 14 mpg

I have never pulled an open trailer any distance with the diesel, my open trailer has expanded metal gate and it is a sail and made my ramcharger drop 3 mpg, loaded 69 Coronet 500 convertible and removed gate and mileage went back to the 12 mpg I got without the trailer