I see a puff of smoke at start-up in my '87 300D Turbo. I had a valve job (new guides) and still see it. I attribute it to the idle adjust circuit kicking in or for some reason the engine just runs rich briefly at startup. It doesn't bother me, I believe the OM603's just do that normally. GSXR or Hatterasguy might have some input on this too.

FWIW mine uses less than a qt of oil (AMSOIL 15W40) per 1500 miles or so (255K on the engine.)

BTW my smoke appears darker maybe greyish, but I always see it out of the rear view mirror, so not so sure exactly what color it is. I could have someone start it while I sniff it - burning oil smells "oily". Unburnt diesel smells like diesel.
Oh yes, one more thing, do you keep the level at half way point (mid scale) on the dipstick? There is good advise in the 'Forum against filling it to the top line as oil consumption is greater if kept topped up,

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!