After seeing good UOAs with Schaeffer's Supreme 7000, a blend and GC posted on this board, I do not know what makes an oil perform well. On the one hand, Schaeffer's has a great additive package and outperforms most synthetics. This seems to vaidate the argument made by Bob and others that it is the additive package that counts. On the other hand, UOAs with GC have been outstanding. I have never seen a bad UOA with GC. GC appears to have a normal additive package. However, on Castrol's website it says that GC (Castrol SLX) creats low wear at start up. This makes me believe that it has a high ester content that makes the oil cling to metal thereby reducing wear. In other words, its GC's base stock that reduces wear. What makes a good oil? A good additive package? A good basestock? Both?