Remember when the company that rhymes with crime had all left lane trucks? Hardly ever needed to pass one. Times change.
Takes alot of tinkering to get the econo up. nitrogen instead of air in tires .1mpg setting the side flairings right so they are smooth for airflow .05 mpg, extending the back flairings a couple inches .1 mpg shortening the distance between the front of trailer and cab back .2mpg. shifting manually not electronically 1 mpg, using the engine torque instead of HP on grades about .3 mpg. Using your head instead of your ### priceless.