I just sold my 2001 Silverado, dually, x/cab,4x4. I took the truck from Indy to Norfolk Va. the first week I had it and running 75-80 mph and got 16mpg. When I got there just going around town and some expressway it jumped to 19mpg. I have checked it 2 times pulling my Cigarette from Indy to Lake Cumberland and once to LOTO and got 13.1 mpg. I went to a weight station and the trailer with the boat on it weighs 14,040 pounds.
I ordered a new 2003 that was built last week and should be here any day. Thats how much I like the Duramax.
Have fun with your new truck. Doug