2003 5.4 expedition oil problem

[stang-1967]

I have switched to mobil 1 5w20 on my expedition. it has 120k on the clock. I am putting in a quart about every 1500 to 2000 miles after the switch. I have had to add oil 3 times now. I have had the mobil 1 in for about 10k. I have no leaks that I can see on the engine. Nothing on the driveway. No smoke from the tail pipe. Where is the oil going and what is causing the problem.

[goon]

try a new pcv valve. cheap and usually the problem.