straight from the manual:
Specified engine oils
The quality of the engine oil selected has critical
significance for the operation and service life of
an engine. BMW continuously approves specific
oils after confirming their suitability for use
in its vehicles with extensive testing.
Use only approved BMW High Performance
Synthetic Oil.
If you are unable to obtain BMW High Performance
Synthetic Oil, you can add small
amounts of another synthetic oil between oil
changes. Use only oils with the API SH specification
or higher.
Ask your BMW center for details concerning
the specific BMW High Performance
Synthetic Oil or synthetic oils which have been
approved.<
You can also call BMW of North America
at 1-800-831-1117 or visit this website:
www.bmwusa.com to obtain this information.
Viscosity ratings
Viscosity is the oil flow rating as defined in SAE
classes.
The selection of the correct SAE class depends
on the climatic conditions in the area where you
typically drive your BMW.
Approved oils are in SAE classes 5W-40
and 5W-30.<
These oils may be used for driving in all ambient
temperatures.
i know in the later model e39 manuals, it mentions mobil 1 5w30 may be used as an alternative.
i also know some people have called bmwna, and they've mentioned that mobil 1 5w30 is ok. that said, i also know that bmwna is not always as specific as they should be. i already know that mobil 1 is fine for topping off, so this is what they may be referring to since they're most likely assuming you take your car in for service, including oil changes.
anyway, as i said earlier, i think mobil 1 is a fine oil and that your car is not going to die all of a sudden because you used it.
btw... i've also sent a message to mobil asking why mobil 1 5w30 is not LL-01/04 approved. i'll see if i get any type or response back.