I own a 2007 Jeep Grand Cherokee CRD (WK in the US - the engine is the MB OM642). I've had it for 13 months and put 10K miles on it. I split my driving about 50/50 between the Jeep and the Jetta. The Jetta is loads of fun, gets terrific MPG, and all that other stuff we (as owners) know. The Jeep is loads of fun, gets terrific MPG (for a 2.5 ton SUV), and is NOT easy to find support for (thanks to jeep forums I am armed with information and knowledge is POWER).
The new Jeep Grand Cherokee is not an MB engine, is not shipp[ing the US yet, and I have no first-hand knowledge of it. But what I read form the OP is this is the MB engine we're talking about.
OK the engine is the same as found in the Sprinter CRD, and other cars, but being that it's in a Jeep it has unique fittings. The air intake is unique, and in some owner's eyes, flawed. Many owners modify it to reduce (or eliminate) the amount of blow-by oil that gets sucked into the turbo then forced into the intercooler, and is associated with the failure of the swirl motor. There are different options to address those issues with - some are legal in the US, some not. Mine is stock now but I'm looking at making some (legal) mods.
Also Chrysler did a lot of things to make it smooth and quiet, but at the expense of efficiency. They never went back to upgrade the tuning for it, so most owners (myself included) purchase after-market tunes. OEM, the Jeep seems a bit anemic. Tune it and it comes ALIVE! It can be flashed via the OBD2 port. I keep my tuner onboard so I can flash back to stock if required (I've never needed to yet)
I have not dyno'ed mine with the tune but others have done theirs, and report BHP of 250, torque of 450ft/lbs.
I have recorded MPG of 29 BUT with the rear gears being so low (3.73) that's @ 45 MPH.
Normal driving @ 2300 RPM (65 MPH) I get about 26 MPG. The EPA ratings for OEM were more like 22 MPG HWY and 18 City.
It can pull a house off it's foundation, or tow a 7,500 lb trailer. It can get from 0-60 in 8 seconds. I can go 550 miles (maybe more) on one tank of fuel. It does not require DEF; rather it uses post-combustion injection to regen it's DPF. It uses it's glow-plugs to get the temps up for regen (another controversial "feature")
and there is so much more to them, but I have to get back to work now.....go check out what the Jeep people say about theirs! most if not all will tell you it's a GREAT car