I had a similar issues with my E70 due to short trips during winter, small oil leaked if the car has not been driven for a while, took it to the dealer, they confirmed it was a faulty oil separator/CCV and replaced a new one. Hasn't had any problem since then.

3 months later, another oil leak again. Is this a common problem for all BMWs?

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'07 X5 3.0d - Black Sapphire Metallic / Camel interior
Specs: Sport pack, Executive, 7 Seats, OEM 336, Hifi
Mods: Aero Kits, Titanium grilles, 4.8i exhaust, Tinted, ///M Footrest, OEM Sport pedals, OEM Rubber mats, OEM Sunshades, LCI Taillights