Nothing.
I purchased my first MB in 1960, 190db, '67 - 200d, '75 - 300d, '87 - 300 turbo diesel, '98 - turbo diesel. In the 39 years, I have nothing but the best experience with them all. I have kept a spreadsheet on every penny spent on them ie: fuel, repairs, mpg, etc on each vehicle. The '98 is the crowning glory of my 40 years of driving in this Chariot of a automobile.
I own a 1997 Mercedes E Class Elegance and I do agree that they are a fantastic car, I have owned two other mercs and I would never go back to another manufacturer.
I have driven preowned Mercedes since 1977 and have owned about 15 or more of them. I have never been disappointed.
In 1999 I purchased a new E300 Turbodiesel. I've been on cloud nine ever since. It is, to my mind, a perfect automobile. It's fast, economical (40 - 45 mpg), and it never breaks!!! It's roomy, sticks to the highway, and has a cruising range of well over 700 miles (1100 Km)... and that's a whole days' driving!!!
Joe.
I owned a Mercedes Benz E300 Turbodiesel Avantgarde Designo with all options you can imagine, it was a dream to drive.
Running costs maintain low and ASSYST warns you when to go to the nearest Mercedes garage. I drove around 30,000 miles a year as a businessman, the only disadvantage of the E class is that they are losing enourmous value after 3/4 years. That's why I bought a new W220 S400 CDI Long, still.
Still the 300 Turbodiesel engine with 177 hp was tuned to a 217pk with increased Nm. I also loved the 300 TD, in 1995 I owned an S300 Turbodiesel, same performance. only a size bigger. For the executive businessman I recommend the 300 TD or an S300 TD.
Have had 2 e class in the last few years. My current E300td is an absolute dream.
That 1975 300d was the best car you had, should have kept it. The w210 will give you problems, you have been very lucky.
If you want a diesel car, Mercedes is great. For petrol cars, especially new models, this is not the case. This is my experience as a car mechanic and owner of a MB 190E 1.8 manual. Constant problems with the injection. Everything else is fine and bulletproof. My previous car a Hyundai Sonata, high miler, never put me in trouble in electrics and injection.
Be careful with rust and automatic transmission in used vehicles. The automatics are not so common in South Europe. From my experience, today a petrol Mercedes is not better than a much cheaper Japanese or Korean car in reliability. MB is the most safe car in the world!! That's why it deserves the glory!!
By the way, MB looks simple car to fix. It is not!! There are many tricky things during repairs, and needs experience. MB dealers are not always the solution...