Fleets can do a variety of things to control their freight efficiency. But one thing outside their control is weather especially wind and temperature. Both of those elements can impact how much fuel a truck consumes.
Headwinds and crosswinds reduce truck fuel economy by increasing aerodynamic drag. Drivers heading in an east-west direction are almost sure to run into crosswinds and headwinds. In fact most drivers will have to deal with wind of some sort because in the United States at any given time there is a 7-mile per hour wind in some direction.