I'm only adding this as comparision...
I have a 14 Ram 2500 CTD Mega Cab. Heavy truck. New front and rear suspensions in it for 14. I had a 10 with the 6.7L before in a 3500 CTD Mega Cab. It was deleted and had a Mini Maxx on it set to about +70hp. I don't drive stuff overly hard. On most days, a 40/60 split of city and highway, empty, I could net about 13-13.5L/100km or about 18mpg.
14 with DEF, no deletes, runs a lot better. Little weaker on the bottom end, but fuel wise runs a consistent 12 L/100km or close to 20mpg. On a few long highway trips, I've seen low 10 L/100km averages (23.5 mpg).
8-9 L/100km is fantastic. We have a 08 Jeep GC with the 3.0L Mercedes and it is a little shy of 30mpg plus it's lighter.
I know a few people who have the air suspension up here in Sask. It gave them greif in winter. It didn't seem like the system liked extreme cold temperatures. Some challenges in holding air pressure at low temps. I'd still get it if I had the option on the bigger trucks.