what truck have the best mpg

The most aerodynamic production truck was a truck of the past, you might be chocked but the 1989, 1990 Peterbuilt 372 with a C 10 or 3176 did 9 mpg with 78,000 lbs, don't remember the speed but I think it was 60 mph, now flame on.

 

Generally speaking trucks that do not have a long nose in front are the best aerodynamic vehicles. However which truck gets the best mileage varies mostly on the driver.
Another matter to consider is that not all trucks, even though they look the same and have the same components do not achieve the same fuel mileage.

 

werner drivers are getting awards from the company for getting 9 mpg...no clue how...

 

Paying out of pocket for a little fuel? I used to drive for Boyd Brothers and it was pretty common for guys to put in a little fuel themselves at the end of the month to get their average up enough to get their fuel bonus. Better yet, maybe they're stealing it...

 

I used to lease to a company (small Company 68 trucks) that tried this with the company drivers in an effort to save money and after a wave of small accidents and the prizes and bonuses weren't enough to compensate for the driver to buy diesel out of his pocket, but still some did try and were caught right away talk about 1991 to 1993 non electronic engines always maxed out all over California, Nevada, Arizona and Utah and some of them clowns were doing 10 and 11 mpg, probably stealing from other drivers while at sleep.