i get about 14 mpg on strickly highway driving at about 80-85 mph but that is the best i can get drops considereabley around town.
ps. that was when my truck was stock. after a chip mod you should get less fuel milage depending on your program.
as take into consideration i only have about 1800 miles on the truck. i test drove a hemi ram and the best highway milage i saw (according to the trip computer) is about 12 mpg on the highway at 65 mph.
the lightning is a very cool truck but if you are concerned about paying for the gas . you most likely cannot afford to own the truck. i mean all full size pickup trucks are gas hogs highway or not.