Though the average tractor trailer fuel mileage of between 7 to 8 miles per gallon (MPG) may not seem impressive, it's a vast improvement over older designs that rarely saw better than 2 to 3 MPG.
Turbocharging increases a truck's fuel economy by applying torque only when it's needed. Modern turbocharged trucks regularly get more than 2 MPG better than identical non-turbo trucks.
The pointier the truck is, the better fuel economy it will get. A good example is the Kenworth T2000, whose long, pointed snout helps to increase its fuel economy.
Trailers that are "boat-tailed" (tapered at the rear end) are known to increase fuel economy by as much as 10 percent over traditional "box" trailers.
The newest generation of automated manual transmissions consistently outperform manual transmissions of the same design, yielding an average 15 percent improvement in fuel economy.
Travel through very mountainous areas requires an engine which produces more torque for optimal mileage.