This is my first post and I need help; after I did my first oil chnge (used Castrol 5-30 Syn), I would get a valve
rattle upon start up randomly, next I changed from a Fram filter to BMW and it stopped temporarilly but, continued later. Now I just changed the oil again but this time I used Mobil 1, (5-30) and I get a hard knock at start intermittently. Should I go to a heavier oil? ('01, 4.4, 80k).