What Brent said..............
The only other thing that comes to mind right off would be if you have a PCV system in the car and it connects directly to the intake manifold, the PCV valve could be sticking and sucking
oil into the intake runner, but that's a long shot.........
Odd that it's coming out of one side and not consistant.....
If you do a compression test, run all cylinders, then come back and give a couple of squirts of motor
oil in each cylinder and run again, if the compression goes up, it's the rings, if the compression stays the same (and it's low) then it's the valves.......
David