I wouldn't consider the mileage drop too closely, in fact I would have expected a 2009 to drop even more to be honesty given its already a huge fuel hog compared to the 6.0. Having said that I do agree the 2003-2007's do "look" a hell of alot more aerodynamic.It's funny you posted this, a buddy and I were talking about this the other night, after a 60 mile drive straight into a pretty bad head wind. He has a 2009 and his milage dropped about 1.5 and my 2006 only dropped 1.1. I know this means nothing but from looking at both trucks side by side, they 08+ frontend looks quite a bit bigger. We also looked for the drag coefficient of both trucks and could only find the 2012 specs.
Any how I think the 05-07 should be lower than the newer trucks. I could be completely wrong to.
Probably not as much a the mud flaps I have to add to pass a safety inspection because of my lift!Stacked on stacks of stacks of stacks that stack....
Sorry I had to
But back on the topic. How do you think a 6" lift would affect the Drag Coefficient?