[Undead Rado]

Those old mechanical Cummins 4 banners are very efficient motors. I'd actually venture to say that they're more efficient (fuel mileage wise) than any new engine. New diesel engines are just getting choked out with cat converters, EGR, and DPF filters. I'd be surprised if these new GM diesels in the colorado/canyon get more than 30 mpg from the factory. However, with aftermarket mods I could see that it may be feasible to push the 30 mpg barrier.

this, my 2010 hd dmax gets about 14mpgs highway 75mph, if you baby it 65-68mph it gets about 16mpgs. remove all emissions with some power mods and 22-23mpgs out of a 7,000.lb 4wd crew cab dually. but from all the emissions crap i don't see one getting 30+ from the factory. my 2010 is the 365hp 6.6 with just a drop in filter, 9hp gain, it will roll right with the 2011's+ with 397hp because they have so much more strain from emissions junk and loose so much power before it hits the ground