I got an oil change for my 335i (2007) at the BMW dealership. Typically about 150 bucks but used an online coupon for San Diego BMW making it $79.95 ... link here http://www.bmwofsandiego.com/value-service-pricing.aspx
Anyway, the service sheet said they used Pennzoil Synthetic. When I asked the service manager about it he said their bulk oil is Pennzoil Synthetic though if you buy individual quarts from them it is Castrol Syntech.
I specifically asked him if the Pennzoil meets warranty specs and he of course said yes.
In my experience with other cars Pennzoil oils have been as good as any other and generally less expensive.
In fact anyone who need oil now, here is a coupn from PepBoys i just came across at about 6 bucks per quart... only good thru the end of the month though.