Just got back to Fresno, CA from Dave Smith's dealership in Kellogg, ID. So my new 2007 GMC Classic is now broken in. It's a 4x4 3500 SRW Crew Cab. It's the easiest driving, most powerful diesel I've ever owned. Driving home thru the mountain passes that never got over 25 degrees, I averaged over 18.5 m.p.g. Phenomenal!
I had 2 Dodge Cummins before the GMC. I was SLOMO on the TDR forum. As you can see by my signature on this forum, things have changed.

Congrats on the new truck, just wait until it gets broke in. You will get even better fuel milage and more power.