Note the graph and how Mobil 1 fairs....note how Castrol is close to the almighty AMSOIL. I'm not one to believe in synthetics as a cult....but from what I've seen about real data, AMSOIL has the best and most open information. Everything I've read on Mobile 1 is a bit too tongue in cheek.
http://www.performanceoiltechnology....oiltesting.htm

Four Ball Wear (ASTM D-4172)

The Four Ball Wear Test determines the wear protection properties of a lubricant. Three metal balls are clamped together and covered with the test lubricant, while a rotating fourth ball is pressed against them in sliding contact. This contact typically produces a wear scar, which is measured and recorded. The smaller the average wear scar, the better the wear protection provided by the lubricant. As shown in the graph, AMSOIL Synthetic 10W-30 Motor Oil produced the smallest wear scar of the tested lubricants.



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Four Ball Wear (ASTM D-4172)[/IMG]