On LS1 where was a user named Patman that does oil analyst for a living and basicly he said that, all the real synthetics (Amsoil, Redline, Royal Purple) are "about" the same they out perform every other petrolum based product "Hydrocracked" or "synthetic blend". Each excel a bit better in certain areas but generally they all kick ass in comparison.

I go with Amsoil because they have been around the longest and I only like changing my oil every 7.500 miles or so.