Hey. I have an E36 318. when it came time for my first oil change i called the dealership and they told me to use a mineral oil. that would be just fine, but my engine had over 200 000kms on it and i wanted more protection. i talked to a phew mechanic friends and did a little research, i wound up useing Castrol Syntec 5W/30. http://www.castrolsyntec.com/
It is awsome, a little more expensive but it is definatly worth it as the car is worth the money. perfection and cleanliness is key to being a BMW owner, and you'll want to take as good of care on the outside as the engine.
Hope this helps your decision.