Its one of the Head or the other GASKETS, have gone.. Look for "Blue-ish Smoke from exaust if it is beeing burnt by engyne, or look for external leaks.. Also look in to the COOLENT to see if it is mixing with it..
OR it might be the SUMP NUT!! Hit those HUMPS?!!!
(I had to replace the OIL COOLER Gasket on my Omega at 90,000 Miles (after I bought it), and the Rocker Cover Gaskets recently..
I hope this helps
Roy
roy, May 2005