Burning Major Oil HELP!
My 03 Nissan 350z with a little more than 115k miles started to misfire on two cylinders and burn a lot of oil. My coil packs are all good, good spark plugs, good fuel pressure, and good fuel injectors. When I did a compression test the results were 175-180 on all 6. I gave it to a mechanic and he found that my CATs were all burned out and clogging my exhaust. So he just straight piped it for now... It also smokes a lot, it's white smoke but it isn't burning any coolant. My oil always seems to be low so I just add a quart every time I need to. I can't figure out what it is neither can my mechanic. He say that it is also running very rich. Could it be a Valve Cover that's leaking oil into my spark plug holes because I did see some in cylinder 6. Also could it be a valve cover gasket? Or worst case could it be my piston rings going slowly. Any suggestions appreciated. Thanks