We have the Mercedes V6 pre DEF.
I have 145,000 miles on the 2007 ML 320 CDI which has had a few gasket issues recently, but no mechanical failure. Repairs after the expiration of my seven year, 100,000 mile warranty can often vaporize the credit card to just replace a gasket or a front remanufactured air shock. I ignore the recommended longer service interval and change oil and filters every 5,000 miles and do the other services when suggested by either the schedule or the deal mechanic from visual inspection. I was able to get over 100,000 miles on the original brakes because of all the long distance driving from multiple trips across the USA.
In October 2012, this car towed the 2013 25FB home through the mountains on I-10 between Los Angles and Phoenix. Unfortunately, after loading the trailer for camping and with my wife also in the car, the CAT scales showed overloaded axles and exceeded GVW so it was retired from that job.
In July, I drove it from Phoenix to New Jersey towing a U-Haul trailer with tires and parts to pickup the 23D. I went from Lakewood, NJ to CanAm in London, Ontario to get the Hensley setup tweaked. From there I drove the rig to Paradise, TX for the modifications and several months later drove the rig to Phoenix through the mountains. That was about 2,800 miles of flat and mountainous driving with a max speed of 65 mph. The engine would drop gears and could maintain the set cruise control speed. One must be aware of how hard and long one pushes the rig on climbs to preclude overheating the transmission. Wish there was a temperature gage for the tranny.
The power plant had no issues. The 23D is both much lighter and narrower than the 25FB so there is less wind resistance. The way the car handles this load, I think it is the perfect fit for the ML.
My wife's 2009 E320 CDI has about 40,000 with no issues to date. It lives the typical spouse local stuff, but where we live, a trip to the grocery choice is at least 20 miles each way so the engine gets throughly heated nearly every trip.
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC
TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell
2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels