You are doing everything correctly. Very unusual!
Likely valve stem seals or oil rings (btw, these will not show up on compression test--what is your mechanic thinking?).
How does the inside of your tailpipe look?
Might be best to keep adding oil and run with it.
someone beat this car when it was new, or was neglectful on oil changes badly.
Last edited by Stinger9; 12-16-2012 at 03:26 AM.