So Chad said that 17.5mpg in an '05 CTD was high so I decided to see what would happen if I drove it like a normal person.
I reset the meter and went on a 153 mile journey with a 500# snowmobile in the back for half the trip.
Here's the results...
This is a 2005 Dodge 2500 CTD/Auto/4x4 Long box crewcab with a Bully Dog Triple Dog with Outlook. I was driving in the towing mode which is the optimal fuel setting. Speeds were varied from 40-70mph and a few stops for in town traffic.
I can't assure it's 100% accurate but even assuming a maximum 15% error that still gives us over 17mpg.