[JimD]

I use BMW engine oil for probably the same reason you want to use a BMW product for the transmission and rear end. But I suggest that BMW makes this pretty impractical. Red Line products are readily available and very good. Mike Miller - who writes the maintenance column for the Roundel magazine - also recommends Red Line (he uses their engine oil in his personal vehicles). As I said above, I used 75W90 red line for the rear end and MTL for the transmission. It works well. It is still not very cold here but it shifts well (we haven't gotten much below 50 degrees F yet.

If there ever is a problem with the rear end or transmission I may have a bit of a hassle because of the non-BMW fluids. Legally this can only become an issue if the dealer can show that the non-BMW fluids caused an issue. I do not worry about it because I think Red Line products are better than BMW products and because an issue with a rear end or transmission in the first 4 years is extremely unlikely.

Jim