Danged if I know... It 'could' be cosmoline.
You say it only happened when you first got it and after oil changes?
So does it go away and how long does it take if so?
Who is doing the oil changes and are you sure the proper amounts were put in?
Might be the pressure from fresh oil but that's a stretch.
If you take it in, it should not be a very long job. No more than a couple hours.
