Well it could be many things. The 2.5L engine is known for having head gasket issues but not so much in the 2006 model year. You could also have a clogged PCV valve, worn valve guides, or indeed some internal damage to the engine.
It has to be either leaking or burning.
Putting it on a lift should reveal any leaks. If there are none, then I'd remove and clean or replace the PCV valve, then if that reveals nothing, do a cylinder leakdown test and see what's up with that.