Doubt if knock is oil related, but probably fuel related. The level sensor allows the oil to drop APPROX 1.5 qt before warning lamp comes on. The dipstick is 1 Liter from hi to low. Many times light knocking/tapping noises can be related to fuel quality, which can vary from fill-up to fill-up even at same station. Some of the early 606 turbos had oil pump noise on start-up, more of a growling noise. Are you following FSS or doing in-between oil changes??
[This message has been edited by M.B.DOC (edited 11-07-2000).]