I am only getting 12 mpg at 75-80 mph with my truck. I have a 50 mile commute everyday and that is what I am getting. It has 2500 miles on it and I just had it into the dealership complaining about it. There diesel tech hooked up to it and said everything looked good. It seems to run good. The engine fan seems to be engaged alot when I take off from a stop light or even when it is cold sitting there idling(you can hear the roar). Any ideas?