Here is the link to a really good thread, IMO. The first half is about filters and the second is about oil. It should answer all of your questions.
http://www.xoutpost.com/bmw-sav-foru...ngine-oil.html
0w-30 is not the SAE recommended by BMW for any e53 that I am aware of. Oil has an API rating and an SAE rating/weight. You need to be sure you are using what BMW recommends for both. (Actually, you will see in the the above attached thread that newer API's can supersede what BMW originally recommended for your car due to advances in oil technology).
Open your owners manual to the index and look for oil. Go to that section and it should tell you what SAE is recommended for your particular year and model. 10w-40 or a 0w-40 is common for a 3.0/4.4.