I'm in the 5.5-6 mpg with my W900 but I'm loaded 90% or the time and grossing 105,500 pulling a set of 40/24 flatbeds. truck has a E model cat, 13speed and 3.55 rears. Also have a tune from Haney in the ecm and a pdi manifold and different turbo. I run in the Pacific northwest and pull a lot of hills. Fuel mileage has more to do with the driver than anything else. A friend runs a 67 925 model KW with a cranked up big cam, 13speed, and 3.90 rears and pulls close to seven mpg grossing 100,000 on a 4 axle 53' flatbed. I will say it drives me nut to follow him though. Takes him forever to get up to speed and he never goes over 62mph. Says he never pushes it past 15 pounds of boost. I told him he was full of it when he told me his mileage till he showed me his ifta.
