I see a few days of Quaker State Ultimate Durability with a filter for $20 left at AAP. It amazes me how much cheaper Quaker State Ultimate Durability is than other syns. I used to use M1 exclusively 15 years ago, then found PP cheap with rebates, then found Quaker State Ultimate Durability ridiculously cheap, then found NAPA Syn cheap. Some conventional Havoline and Quaker State Conventional for $2/qt once in a while, too. I just don't remember a Syn oil always being that much cheaper than others years back. Anyway, thought I'd share if anyone needs to stock up...