I can't speak to any om648 issues but having 2 w211 08 09 e320s and a w210 e300 in the driveway I CAN speak to those. If I were in the market for a diesel E class, I would FIRST AND FOREMOST find a shop to work on it if I didn't want to take all the time to learn to diy everything. I have found that most of the shops around me would MUCH prefer to wrench on korean junk or 30+ year old American stuff than euro diesels with computer management and emissions stuff. The smug dealer even looks at us with contempt. For example I was very angry that EVERY car ready for pickup at the Richmond, VA dealer service area had been washed and vacuumed EXCEPT MY 08 E320. When I asked about it, I was told "oh well if you want to leave it overnight we can get to it tomorrow" but that they would also "detail it" and have it ready by "End of Day" if I wanted to pay for it... F those guys. So get a shop first.

Next find a good car. These are old cars so try to get one with reasonable miles. 100K is ok, 350k not so much. And remember the older model with be less complicated BUT will be older- so while the motor may be rock-solid (E300) the rest of the car is getting old and things are breaking down (motor mounts with magic fairy fluid inside perishing, window regulators broken in the down position, biodegradeable WIRING HARNESSES- I guess so you can throw them in your compost pile or toss them in your salad or something because you know conducting electricity is totally over-rated.)

Next suggestion- set aside some money to fix the things it needs, and WILL NEED! So, for the e320s we have, if I had to do it all over again, I'd figure into the purchase to add about $4K and after purchase, immediately take it somewhere to get the stupid $2500 oil cooler O-Ring repair done, but also the valve cover gaskets, the turbo inlet gasket, get the EGR cleaned out and keep funds ready for the swirl flap motor and the stupid turbo actuator that will fail around 100k like mine, if it hasn't already. Also know that you DO NOT want air ride unless you intend to get that repaired or replaced as well, and realize that at 15 years all the rubber junk used in the suspension will begin to fail. My 08 has the notorious "clunking, popping" front suspension noise and everything has been changed but the struts and torsion bar with attached bushings and end links, which will sadly be next. Until then my wife will not ride in it because the banging and clunking when I brake or turn scares the hell out of her. I don't drive it much because the turbo actuator is out so it's miserable to drive and slower than the e300 on a bad day. I bought it at 80K, so I had a pretty good 10K I guess. Her 2009? Its got 280K on the clock..

Having said all that it's like the guys on Top Gear would talk about from time to time. Owning some cars is like being in a relationship, not quite like a marriage- because over time, that is probably less expensive. But there will be good and bad in MB diesel ownership, like in a relationship, that you deal with over time. Dealing with the bad somehow makes you appreciate the good even more. And I LOVE my 08 e320 diesel. I love the 30+ mpg, I love hitting the pedal on the on ramp, dropshifting and rocketing on to the freeway, the comfort of the ride, and the beautiful looks of the car. But I also know after all these repairs that she's higher maintenance and if I had known to use some prophylaxis, or if MB had done it for me ahead of time if I'm honest, I would have had an even better experience.

Goo Ruck... -J