My truck is an 00 3500 4x4 QC with the 6-spd (NV5600) and 3.55 gears. I can still get fairly good numbers imo (17-18mpg) in the winter going down the highway. However I get these numbers with nothing in the bed, going 55mph in overdrive, and watching how fast I brake/accelerate.We have a 02 Cab and Chassis 4x4 flatbed witht the h.o. engine and a 6sp. manual transmission and 3:55 gears. Uncle is complaining that he is only getting 15 mpg out of it even on extended trips on the highway. It is 100% stock.
What can we do to improve mpg? We have a new air filter. We also have a superchips programmer on the way. Should we open up the exhaust or any other ideas?
Acceleration and overall road speed are going to be the biggest killers of mileage in a truck this size with the aerodynamics of a brick.
It's pretty much an understand rule that for every 1mph over 55mph you can expect a 1% drop in fuel economy. However this is a rough figure you will actually start losing mileage even quicker past 65mph.
So convince him to enjoy the scenery and drive slower and see what he gets then. If it is still low after that you can probably blame winter fuel. However I would check the obvious. Tires, alignment, brakes, etc...