190E's of that time frame, as well as most other MB of the period, were susceptible to valve seal wear. The seals are rubber (a Viton type rubber) elements at the top of the valve guides that are in rubbing contact with the valve stem, so they will always be an eventual repair item, it is just that they failed on these cars a little early, and the failures were very consistent.
Anyway, when the seals get old and stiff, they cannot effectively seal the engine oil away from the intake valve area, which is under vacuum. Consequently you suck oil into the engine. Usually valve seal failure in these cars appears as a sudden increase in oil consumption.
The good news is the job is not too expensive and there are many mechanics familiar with how to do it now (you do not need to take the head off to do this, which makes it a shift instead of a few days) and the seals are dirt cheap.
I had it done to my 190E 2.3-16 when the consumption suddenly went to about a quart every 700 miles. I also noticed some smoke coming out the tailpipe. On my car the job is substantially more complex than most 190's as the camshafts have to come out to gain access to the valves. I paid about $700 to get the problem fixed at 70,000 miles, and ran for another 135,000 without any further problems. Yours should be quite a bit less costly if the problem is valve seals.
From what you describe, I would do some additional investigations and make sure I had the problem identified, like a compression check, pull the plugs and look for evidence of oil, and so on. My guess is valve seals though.
Hope this helps, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)