Several independent tests that were exhaustive (Lubrisity, friction wear, sheer testing, viscosity breakdown, metal contents, etc.) (Don't have the time to dig the old thread out) Studied alot of oils through 10,000 miles. They were in order. Amsoil, Mobil One, then Royal Purple up to 5000 miles. Then as you approached 10,000 the Crown switched to Mobil One. RP still in 3rd. So for the price, IMO Royal Purple is overpriced. Bottom line of the tests though is none of the name brand synthetics outclassed another by a definitive measure. So I buy whatever is the cheapest at WallWorld when I need. Oil is oil. And when you start with quality stocks to begin with, the rest is chemical slight of hand Advertising BS.