The Redline stuff is excellent too. I used their ATF in my 5-speed. Great stuff. Anything under a 20W50 sold for street use has been changed to meet newer requirements. I used Brad Penn oil for breakin and flat tappet cars. Newer cars with roller lifters don't need near the zinc an older car does. Mobil 1 'Racing Oil' still has all the zinc. As for Amsoil, I don't buy test results from a producer of a product. I'm not saying it's bad, I just don't think their results mean much.
It seams to me Valvoline had a good synthetic, but then changed their base stock to semi-synthetic. This isn't gospel so read the bottle. But for me, there is Mobil 1, Redline, Brad Penn (dino) and everyone else.
Did I mention that opinions on oil are like talking politics, sex or religion?