If I were going diesel for heavy hauling/towing I'd go Dodge.  Just on Monday I traded my 2008 6.4 F-250 CC,LB,4x4 with only 67,400 miles.  I was hoping to keep that truck forever, but it started nickel/dimming.

A few co-workers have the new emissions Cummins, 1 a 4x4 2500 gets higher teens mpg, another a 2500 4x2 in the low 20's.  I had to baby my 6.Flop to get 15 local driving, and double dose the power service to get the added cetane boost to burn the soot.  Ford Tech told me Pennsylvania's cetane levels aren't up the Fords standards what the engines were designed to run on.  Reason for the EGR to clog up @ only 63K, that was warranty, but Alternator wasn't a few weeks later.

My 1 nephew had 2 Chevy Emissions Dmax's, He's currently looking for a Non DPF diesel.  He too had a tough time getting the 15 mpg local driving.  If your set on New Diesel, better get a 2010 model, as I understand tighter emissions restrictions for 2011 models.  CAT is leaving the Highway market for big trucks, so that should tell a thing or 2 of how bad it's getting and headed.

 ALSO note Ford has a NEW Engine for 2011 models a 6.7 or something.  Navistar left Ford, so it's only a Ford Diesel, Navistar might have joined CAT in leaving the highway market, don't know, just know they left Ford.