I have never seen independent tests on different brands of oil to show that one is better than another. I think the Blackstone lab results are somewhat useful but they are difficult to use to prove that one brand is better than another as the variables are hard to control and even then it shows that for one engine, one oil seems to have better results than another oil.
I also think the BMW "recommended brand" doesn't mean much as it keeps changing over time and believe it has more to do with a payment than BMW going with the best. I think when my car was built it was Castrol now it is now Penzoil?
I will say that my car runs much better after a complete wash/wax/detail.
