If topping up go for the same as what you have as coolant now.
Otherwise, do a coolant replacement with BMW/OEM green stuff and buy extra for topping up as required.
cheers mate, I didn't know what was in there, just went bmw and get the proper stuff. only £10 per 1.5 litres, I bought 4.5L and it needs to be diluted so 1.5L turns into 3L
