It dosent have to be, but you must put the same grade in and on NO account mix two different types/makes.
But if you want to go for another make you will have to drain the system, so I would have thought its cheaper to just top up with BMW fluid.
__________________ VELVET BLUE UK INDIVIDUAL , IM THE LAST
UNITED WE STAND DIVIDED WE FALL
I stepped in a plate of Pasta the other day - now I have to worry about my Carbonara footprint!