I have a '16 Crosstrek. At 20k I changed the factory fluids and the rear diff was dark and the front golden. Diffs will tend to shed iron on breakin. The small amount of oil in the rear diff will significantly increase the iron ppm over the front diff. I did one more change around 50k thinking this should have drained out all breakin wear. The oil was golden in both diffs. I filled both diffs with Delvac commercial 75w90. I don't think I will need to change any more for the life of the vehicle unless I would frequently tow as that oil is formulated for up to a 500k application.
The key is getting all the breakin shavings out and then your fluid should last a long time.
The key is getting all the breakin shavings out and then your fluid should last a long time.
