Thanks all, for your opinions!

Bcred, I understand you, that is how I normally maintain any of my cars. That being said, I have found (for me) that my BMW is a bit different from Japanese cars, and even other German marques like Mercedes.

In most previous Mercedes, I would do what you do, and had no problems maintaining things on a part-by-part basis.

That's why I originally scoffed at the notion of replacing the whole cooling system at x number miles (pardon the pun). Then after the first few pieces started going, I saw why.

So now realizing that the X5 is the worst built car in the world (just kidding), I am trying to get a feel of the unique maintenance quirks these have. I havent become a paranoid nanny parts changer because of my experience, I still do a cost-benefit analysis in deciding whether to replace a part pre-emptively. To this end, everyone's collective experience is invaluable!

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04 X5 3.0i auto
03 X5 4.6is