oil out the tailpipe - OM616

[herring]

Shortly after buying my car, I noticed that it left a bit of dark smudge on the asphalt where I let it warm up (it was winter, so there was a some effort in starting and a fair bit of warming up done).

I figured that the smudge was soot, what with all the smoke of cold-weather starting. I recently figured out that the car is actually putting a fine mist of oil out the exhaust pipe.
Oil consumption is pretty low, so we're not talking about a huge bunch of oil here...maybe a quart in a few thousand miles. It's hard to tell because I had some engine seals replaced in February, and only bought it in January.
With the warmer weather, there is some gray smoke at startup, and under heavy acceleration. Otherwise only little puffs of gray smoke here and there. Never had any black smoke at any time.

The engine does have about 309,000 miles, never been overhauled. But I did the blowby oilcap test when I bought it (and again over the weekend) and it doesn't even rattle--just tips a bit to the side and lets a flow of air out. Think nice breeze, not Hurricane Katrina.

I have gotten the engine started in the 20s with no help from the block heater, so I figure the compression can't be too horrible.

I guess what I'm asking is, is this normal for an engine of my mileage, and it will continue doing this peacefully until I get it rebored? Or is it something of more serious concern? How much would one expect to pay to have an OM616 engine given its "300,000 mile service"?