You have a W123 Body with a 617 engine. Try driving it hard for a bit and see if the smoke clears up. My 300SD was owned by a little old lady and smoked like a chimney when I got it, but a few full "throttle" blasts cleared it up.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine