Often times when
oil is running down the valve stems (guides or seals), it will continue to run down for some time after the engine is shut off. Then when restarted, a nice puff of blue belches out the pipes. Also when you pull the intake, you should see
oil on top of the valves.
Compression rings (top two) and
oil rings (the bottom groove) work totally differently. It is possible to have good compression and the oil rings not work worth a hoot.