Sorry, I can't keep silent...
If the oil-seals on the valve steerings are worn engine oil seaps through. The symptoms are typically blue smoke when it's started after standing for a while. Run the engine hot, let it stand for 15 min and start it. This problem won't show up as poor compression. The fix are new valve seals.
You should (don't know the english terms here) also wear in the valves in the seats (rotate with carborundum). This does address poor compression.
If there is constant blue smoke, it's more likely the piston rings.
//John