What I find interesting is how much both these products have changed since '09.......Penz more than Castrol, but still. And I just keep using Mobil 1, which has not changed much, if at all.
The argument about castrol pricing is not accurate ...My local Walmarts, AZs, Pepboys and O'riellys sell the valvoline,m1,castrol edge syntec and PP for the same price...the same can be said for M1EP,PU and edge gold...my vote Edge