Oil Level Strangeness - Please Advise!

[dkr]

So, yesterday I did an oil change with my topsider (it sucks the oil out of the dipstick), changed the filter and added new oil. With a cold engine, the oil was just above the low mark. I turned the engine on, let it idle for a while, and then drove it around the neighborhood until it was at operating temperature and then checked the oil level again. It wasn't even on the dipstick! It was rather strange as there are no signs of oil leaks anywhere.

After sitting overnight, I checked the oil again and it was way full on the dipstick. I drained about 2-3 quarts out, checked it again on the dipstick -- it was about halfway -- and drove it around just to get it up to operating temperature. Once again, it was very low on the dipstick although it still did register.

I then added about a quart of oil and it got up to high operating range. So, I turned the car on, let it idle for about 15 seconds, turned it off and then checked it again. The oil had visibly dropped on the dipstick. I am very confused here as I have done this process many, many times and not seen this before.

Here are some additional notes:

- Car is relatively low mileage -- 1984 300D OM617 completely stock -- (under 150K and has been very well maintained).
- I check oil levels religiously every time I fill up and I generally add about a quart between oil changes.
- On the last oil change, I did a UOA (Used Oil Analysis) and it showed practically no wear.
- I put in a brand new OEM oil pan and an OEM skid plate, so my oil pan is not dented.
- My oil pressure appears to be normal and engine is running normal.
- There are no visible leaks. The oil cooler lines were recently done and are completely dry on all four connections.

I have a pet theory on this but it doesn't entirely explain where the oil is going between starting cold and getting to operating temperature. I have not driven this more than what is necessary to get to operating temperature, so it may behave differently if I were to drive it on the freeway for a while.

Can anyone explain where my oil is going and if I should be concerned???

Thanks,

Dkr.