My Volvo developed a metallic rubbing sound near the valve cover. The noise will go away if you take the oil fill cap loose. The PCV system is allowing a lot of vacuum inside the crankcase (engine).
ALL of these cars have an o-ring/diaphragm that MUST be replaced about every 60k miles. It is located inside the oil filter housing. It must be removed from the vehicle, and taken apart to replace the diaphragm. Be careful not to break the plastics, as you take it apart.
The most common problem with extreme oil consumption is the piston design. The rings and the spring is to small. Causes the oil is the combustion chamber and burns it off. Volvo redesigned the piston so they need to be replaced