Ive decided to change my differentials early in my 2008 silverado with 23k miles on it. I've narrowed my choices down to two gear lubes. Amsoil SVG 75w90 and Valvoline Synpower 75w90. Ive used the amsoil in my old C5 vette, and i used synpower in my old S2000 and Rx8 R3. Both lubes performed excellent. Do you guys think that SVG is worth the extra $ per QT over the Valvoline Synpower? It seems Synpower meets all the same specs as the SVG. Planned use is 50k mile intervals in my Silverado, 3:73 locking Differential. I do mostly highway driving as well as light towing occasionally.