I read this on an article:

In 2004, with the facelift of the X5, and technological advances; such as xDrive: a renewed part emerged. This part, appropriately named the "Cold Country Kit" consisted of a renewed Oil Separator assembly complete with insulated valves. We were horrified to find out that 4 out of 5 dealerships we contacted were not using this part to treat the oil separator problem with the earlier model X5's. They were simply replacing it with the original part, again and again.

I've noticed too on the forum that alot of people with the earlier model x5's have more so the oil separator problems.