Amsoil has littered the web sphere with their comparative testing of various oils. They have kept up the game updating charts. I have a few concerns/questions assuming the tests were performed correctly and without twists in the results: (1) they always test 10w30, not 5w30 which is most popular now, we at least I care about 5w30 performance, i can not translate 10w30 comparative test results to 5w30 as is (or should I?) (2) at least for the recent testing, they included synthetics like PP, Valvoline Synpower, but when it comes to Castrol, they only do it with GTX. Why do you think they'd include at least Castrol Syntec, (or for 2009 testing, Castrol Edge) Any thoughts/comments are welcome.