I just changed the engine oil in my 2009 528xi, using Mobil 1 0W-40, a recommended oil that meets BMW LL-01 specs. In addition, a MANN oil filter (they make for BMW). Had 5000 miles on the old oil, at 8 months time. Other choices would be Amsoil European formula, Full SAP, Castrol syntec 5w-30, and of course you can buy oil at the dealer. Stick with the LL-01 oils for best results. I have had engine issues with other vehicles using Royal Purple, and would not recommend that brand. Pennzoil Ultimate is also a good choice in my book. Bottom line, don't buy into the 15000 mile oil change schedule for ANY car let alone a BMW.