外漏:各種油封失效的漏...
內燒:Piston Ring,Oil Seperator/CCV,Valve Stem Seals...
Google bmw 3 e46 series oil consumption,tons of info!
I only use BMW Original Oil and BMW apprved oil with max 8000-10000km oil change interval(factory recommmend 15000km+ change,),so far so good!