Response regarding the use of Royal Purple
I will not use Royal Purple in my BMW. I used it for a few years in my 2003 Yukon XL, and developed a cracked cylinder head. The RP may have contributed to that, and perhaps it didn't, but I have refused to use anything that I used in my Yukon, in my BMW. I will stick with the Mobil 1 0W-40, the OEM BMW Synthetic, and now I may give the new Amsoil 5W-40 European Formula, Full SAP, a try. Thanks.