Both run "specials" every month. Last month Castrol was the special with a Filter (this month it's Valvoline, I think) for a bargain price at AAP, not sure what it was at AZ. But, every month they both have Oil Change Specials. Good marketing, it gets customers in the stores, once there then there's opportunity to sell the customer other goodies.
Yeah I think the 5 qrts Valvoline fully synthetic and filter for $32 ain't bad. I've always ran Mobil1.
Have you or anyone tried Valvoline?