GC every 7.5 k in the 07' X5
 

YES it meets the requirements:
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Exceeds European ACEA: A3, B3, B4; VW 502 00, 505 00, 503 01; MB 229.1, 229.3, 229.5; BMW LL-01; GM-LLA-025, GM-LL-B-025 and the engine protection requirements of ILSAC GF-3 for API Certified Gasoline Engine Oils.
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If you had a pair of socks that would last 15 yrs - would you never change them? They may not wear out but they would certailny get very dirty.
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SO I don't want all that dirt in my investment - so If you plan on keeping the car for more than 3yrs. Change the oil at least every 7.5K and use the
best oil you can get your hands on - I like GC 0W-30.

And what's wrong with bmw oil. Castrol or mobil 1 ? :dunno:

Mobil 1 seems to be a popular (and I guess safe) choice.

You can go with the BMW Synthetic. I haven't seem the bottle for myself to see what specs it meets or exceeds. I think it's rebottled Castrol, but not 100% sure whether its Euro or US-spec, becuase there are differences between the formulas.

The normal Castrol 5W-30 sold on most shelves apparently doesn't provide the same level of protection like a Mobil 1, becuase I've read its not a true synthetic. I don't believe it meets BMW LL-01. The German-made Castrol 0W-30 I recently bought does meet the BMW LL-01, as mentioned on rear label. :)

Dealer oil is CAstrol TXT 5W-30 - GOOD
 

Castrol TXT is the Dealer BMW oil at MOST and the CASTROL GC 0W-30
found at Autozone is = Castrol SLX.
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Both ore great oils that meet BMW LL-01 used for extended oil changes.
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The US branded versions are not suited for extended drain intervals.
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So if you can get the *Dealer oil for less than $6 - what GC is at Autozone, then great.
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Main point - CHANGE your oil at least every 6 months regardless of syn oil
you select & use a quality filter - Dealer Filter or Mann Filter.