The pipes get their oil layer through cutting oil during the thread cutting process. At the same time the oil functions as a protection against rust. To not damage your clothes, we pre-wash the pipes for you. Residual quantities should be able to be removed by using the enclosed cotton cloth. If that's not enough we recommend brake cleaner.
PLEASE NOTICE: Do not use water or other cleaning supplies or rust will be the result - except that's exactly the look you want ;-)