184k on 04' EX 5-speed manual, doing routine oil change (hi-milg synthetic blend) after heavy highway use over summer...barely 2 quarts drained out, not particularly sludgy or dirty; no remarkable bluish exhaust or smoke or unusual smells; running fine...no leaks or abnormal stains near seals or in compartment...lost over 3 qts. in 4 mos? Should i be concerned? I've heard PCV valve or piston rings, etc..where do I start?