Chris, the engine as TTT2 says is the merc workhorse. when merc got jeep , jeep didnt have a decent diesel engined car so merc moved them to graz and opened the parts cupboard for them to dig in.
In my experience its a very good engine.Its achilles heel seems to be injectors but its not a serious problem. You soon know by the dog rough running when they need looking at. Mine is still on 4 out of the 5 original injectors and i replaced 1 last year (paid for by the negotiated discount when originally buying the car :augie ) if it runs well the engine is very flexible and i would sum it up y saying the bottom end grunt handed out by the five cylinders is great. I noticed a massive difference with the 5 pots making up the 2.7 litre compared to the nissan 4 pot particularly with the van on the back.
Im no expert on the ml but i do understand it has a lot of other bits in common with mine. Mines now just under 90 000 (i think) and ive contributed nearly 15 of those in the last year with nothing but 1 injector , a new exhaust clamp and basic routine servicing. ironically its been one of the cheapest cars (touch wood) to run that Ive owned in recent years.
I see that ones well spec'd. Trust me when you sink into the leather seats (or maybe sit on them in the German version?)and play with the gadgets it will bring a smile to your face.
On more practical note we had mls in very basic trim on our fleet for a while. I didnt get to use them thatmuch but was happy to when i did , they were well liked apart from apparently being "too slow" to put that in context it means cant easily do over 100 and are beaten off the mark by an octavia vrs
they always struck me as comfy and would be good as a family car. They spent a lot more time on the road than our range rovers :augie
My jeep , with that engine running through the auto box realistically returns 25 to 30 mpg mixed use without driving like miss daisy. it drops a bit but not enough to worry about with the van on the back though of course as you'll know better than me, there's a lot can affect that.ironically i get better towing mpg than i used to in my old 2 litre mondeo !!!!
Things to look for? on the jeep and i think its common with the ml , the gearbox is a sealed unit (may apply to the manual). You are not required to top up the oil so any leaks or drips, walk away.
The climate control can be problematic on some models. The electronics are reliable enough but the servo motors that drive the flaps and what have you can stick. On a truck the age of that one as with mine , if they're not sticking now they probably wont be going to but check them by switching to manual and give them a work out :thumb2 if there are any problems in that area they can count big time in your favour. the actual workings ie the servo motors are pretty easy to replace but he job is a very expensive labour intensive one if you don't diy as the dash board has to come out.
Have a look on
http://www.peachorlemon.co.uk/ if you bear in mind whingers are usually quicker to post than satisfied punters there is some good info.
I can say hand on heart I am totally satisfied with my jeep which has that engine in it. i'd buy another like a shot (in fact was in the garage just the other week :augie)I have mixed feelings on the looks of the ml but thats personal taste and i still think on the basis of having had some use of one theyre great cars :thumb2