Diesel Exhaust Fluid is used from a separate tank as it is not a fuel. It is used to treat the exhaust so that the engine can be tuned for (among other things) better fuel economy. It's a win all the way around . . except the expense. I read a post by a Cummins engineer on another forum stating that the exhaust/emissions system on a new CTD alone is as expensive as a brand-new Hemi engine and auto trans (make that $15k).
The capacity for work and high fuel economy of the CTD (Cummins Turbo Diesel) set the standard the others tried to meet from 1994-2006, but the addition of strict emissions requirements starting in 2007.5 changed it all. More power, today, but at a higher expense per mile of ownership. And reliability/longevity may not again meet the earlier B50 standard of 350k (250k on GM & Ford).
Perhaps we will see a nice V6 diesel in the half-ton trucks closer in power and economy to the older diesels. Certainly, with around 300HP/500TQ any and all Airstream trailers can be towed by one.
15-17 mpg towing a 25-34' trailer is no small achievement for a truck of any capacity.
1990 35' Silver Streak Sterling
; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 10-cpm solo, 18-cpm towing
Sold: Silver Streak Model 3411