Ive used royal purple 5-30 forever (don't have anyone that sells amsoil around here or I would run that) I notice better fuel econ. and I drive at least 100mi every day.
My 06 had 40k miles on it when I switched. I don't change my oil for at least 20k miles. The same way I explain it to my wife. I may spend like 60 bucks to change my own oil using royal purple. But if I have to change my oil every 3k miles b/c I'm using cheap oil then it would cost me triple what I pay.
I have also read about the wear tests on oil and royal purple and amsoil where the only 2 full syns. to outlast there tests. That's when I switched to royal purple
