Diesels consistently get in the high teens for city MPG and low to mid 20s for highway. The 5.9 is basically the God of diesel engines and is the best choice but with some simple mods the 6.7 can get just as good mileage as the 5.9. But as stated the buy in price is crazy high and maintenance is going to be a bitch unless you're a diesel mechanic
2008 Black Dodge Ram 1500 QC, Big Horn Edition 5.7 Liter HEMI
the 6.7 diesels get horrible mileage due to DPF in exhaust and EGR plugging up the intake and the VGT vanes.
5.9 common rail should be getting 17-24...if yours is not you may have a cracked injector tip.
might want to check out the injectors (they are notorious for cracking tips on the common rail engines)
also once you get that done, get a smarty programmer and put in the mileage tune with high timing. it will increase fuel economy a bit and reduce overall EGTs.
if you want lots of power to go with it, you can go with a smarty, or the now more popular EFILive.
as for economy: I get 14, but my injectors suck. they are smokey as all hell and haze at idle. I need to have them pop tested or just replace them as I believe the pop off pressures are all over the place on them and definitely set way too low...probably at 260bar when they should be at 310bar.
'00 2500 Sport 4x4 Cummins, powered by the ultra high performance 53 block and the never failing SOVP44! 576hp 1285tq 8/10/2013
when i first got my diesel ram, diesel was cheaper than regular, and since then that isn't even close to being the case, the added mileage is great, but i'm starting to wonder how ahead i really am. should i do the math?