I purchased my 95 in 2013. I believe it was reliable the first 17 years but then everything needed to be replaced within 2 years of my owning. At purchase it had 136,000 miles.
2 days after purchase I had to replace the smog pump. Thereafter was the water pump, rebuilt trans, heater blower, radiator, brakes.
This car is very nice but understand that the cost of a part isn't bad but the labor will be outrageous. The water pump for instance wasn't too expensive, the issue was it took 10 hours labor to dismantle one side of the engine to get to it.
Minus normal things going wrong and it just so happened to be after I owned it, it's very well built. Analog clock still works. Everything still works and it's not 20 years old. As of now I have essentially replaced everything but the alternator and battery and it's solid.
Keep this in mind.. My understanding is there are 2 common issues with this model.. 1). The reverse tends to go out and thus a rebuild is necessary. 2). The gel in the motor mounts will solidify and the car when at a stop light will cause the car to shimmy a bit due to the mounts no longer sustaining the shock.
I bought this car at least 3 years ago with 50,000. Yes, 50,000 from a lady in Encino who passed away. It has not given me ONE PROBLEM other than scheduled issues. My Mom drives it and has put on at least 30 to 40k. I cannot express to you enough how well built these cars are.
This is the second 300D I've had I work out of my vehicle 12-14 hours per day 5-6 days per week. I wanted comfort, reliability & economy. I got it in spades. This one I've had 2 years. I've put over 100,000 miles on it and it has delivered continually. You just have to regular maint. I take care of it and it takes care of me. 265,000 and counting.
I recently bought a 1995 E320, I was just looking around because my 1995 Saturn SL1 was starting to have some reliability issues and had just reached 210,000 miles. I was looking at Ford Focus, but the Mercedes E320 caught my eye and after the first minute of the test drive I knew I had found a solid car. My E320 has 155,000 miles on it and I had a mechanic check it out and it was given a clean bill of health. I would recommend one of these cars to anyone who is willing to give a 16 year old car a try.
With the youngest W124 now at 15 years old, you'll have to be picky and discerning when buying on. I found a 95 with only 78,000 miles on the odo. The car has been a joy to drive & own. Try to find one where the previous owner has already done the major repairs: trans rebuild, head gasket replacement, wiring harness replacement. Mine had all those items already done. The looks of the W124 has aged very well, looking neither vintage or new though. The engine performance is still good by today's standard, but not as peppy as cars all seem to accelerate with more pep. My E320 has been reliable and starts up with just one turn of the key every time.
INTERIOR: The interior is well thought out and beautiful. It has just enough flair while simultaneously being utilitarian. The ride quality of this car is very smooth RIDE QUALITY: the suspension is very smooth without being like an old Cadillac. Steering is precise.
No sup much improvements, but quirks for potential buyers to be aware of. The door lock and ignition locks do break. It's best to replace the locks at the first sign of stickiness as you turn the key. Only 15 min repair if caught on time. Other wise, headache once the lock breaks, will take hours.