I recently had my Turbo rebuilt on our Rangie as it wanted new bearings...more of a concern was this oil, however on chatting to the chaps at Turbo technics they said it's perfectly normal to have some oil in there and not to worry...my Turbo needed other work anyway so got the treatment.
Only will it become a concern when the oil getting through is enough to allow the endine to actually run on it's own engine oil instead of diesel in the event of which you have two options....
- Stall it
- Run like your pants are on fire.... indeed if you don't run fast enough they might well be.
So unless it's running oil as opposed to a covering then forget it.
Lee D