Coolant for E39?

[LikesBikes]

Hi all.

Will be replacing my auxilliary water pump soon and find myself wondering which coolant I need to refill the system. Is there an aftermarket brand that meets BMW's spec or is it best just to use the BMW branded one? A nose round the internet reveals some bewildering discussion on this and no solid answers so I'm leaning toward the OEM stuff from the dealer.

Cheers gang,

Darren.

[LikesBikes]

Thanks all, very much appreciated. However as luck would have it I came home and had a poke about and I seem to have fixed the problem (electrical connector not quite connected I think?) so no need for a new aux pump now.

Advice still useful though as I'm thinking she must be due for a coolant swap, many thanks.