Here in Australia, the E230 version of the W210 with the M111 four is proving to be very reliable. An ideal car where outright performance is not a high priority. I believe in the US you could not get the W210 with the M111 and therefore have to choose between the M104 inline six with its head gasket and oil leak problems or the M112 V6 with harmonic balancer problems. Possibly the E430 with the M113 V8 might be worth considering. Anyone have comments of the reliability of these? If the smaller car is suitable then consider a C-class with the M111.

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.