Mixing Ability/Compatibility
WARNING: This page does not describe the selected car, but rather 250 other vehicles, including the 2006 BMW Z4, 2006 BMW X5, 2006 BMW X3, 2006 BMW M6, and 2006 BMW M5. However, it is still accessible from the selected car via links, so may be relevant.
It must be possible to mix all engine oils with each other, even synthetic with mineral oils, without causing any incompatibility problems. A further requirement is the compatibility with all materials contacted by oil, in particular oil seals, hoses and paint.