Just looking for some advice.

Over the last few days I have been getting intermittent "Check Coolant Level" messages. I physically checked the reservoir and sure enough it is low i.e. the red float is not level with the reservoir opening.

I called BMW yesterday to enquire and the the mechanic I was talking to simply said to fill it up using distilled water. Now having read the articles on coolant I was taken aback slightly by this as the 'Fluid Maintenance' article I was reading mentioned distilled water but also the fact that you add it in a 50/50 mix to the BMW coolant product. So I am confused. BMW here in Hong Kong like to sell you whatever they can so they have a vested interest in telling me I need to come in and have it mixed with their 'unique' coolant.

Now I see having read the article that the coolant protects against things like freezing and boil over. Freezing is not an issue in Hong Kong obviously so for the boil over is it true that I only need to add water. I think not and that's why I have done nothing. Can someone please shed some light on this issue.

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2002 X5 4.4i. Black with beige leather interior. Sports Pack.