Here are some fact for those that thing BMW dealer oil is different from Castrol 0W-30.
http://www.castrol.com/liveassets/bp..._Sept_2011.pdf
as you can see on the spreadsheet the 0W30 is the BMW LL 01 Approved. 5W-40 would work as well. The0W30 is the same thing (EXACTLY) that BMW sells at the dealership.
The Viscosity of the oil in 5W 30 is a little greater with a lower variability from cold to hot.
just my .02