I have a 2003 Mazda Protege 5. Every time I start it up after about 6-8 hours, blue smoke comes out the exhaust. It burns through about 2 quarts of oil a week. We have replaced the PCV valve twice, put on a whole new head with all new valve seals and everything, new spark plugs, new head gasket, and checked the compression of piston rings. Compression is fine. We found that oil was in the PCV valve and draining into the intake manifold. Took out spark plugs and took a flashlight to look down the cylinders. There is a pool of oil on top the pistons in each of the 4 cylinders. Please help! What else could it be?