Royal purple clearly seems to be the one to go with from those tested. One of the reasons I've always liked Amsoil is that they actually do a standardized version of the test themselves and publish the results. Check out the four ball wear test results for their 5w-40 at:
One problem with that test is that they didn't compare apples to oranges. Some of the oils were 0W40, some 5W40, at least one was 15W50. I also didn't notice if they specified that they heated the oil of the temperature that they tested at.
It also didn't test for the oil breaking down over time.
I have read time and tiem again people who have has forced induction cars that refuse to use Royal Purple after bad experiences.
Just what I have heard. Also, most of the oils in the US, while sold as the same name, are different than their European counterparts. One definate example of this is the Castrol Synthetic line. The european formulation is vastly superior...
I'll stick with my Motul 300V Chrono 10W-40 for the meantime. For those that don't read the above link, Motuls line was that the test was suitable for gear oil not engine oil. A comment I tend to agree with, what is the point of testing an engine oil for conditions it is not likely to see? The damage shown to the test bearing if applicable to internal combustion engines would surely have resulted in millions of engine failures in cars running cheap and nasty mineral oil.