I found the last 5-quart jug of Mobil 1 5w30 at my local Wal-Mart, mixed in with the 10w30 jugs ($17.88). Of course, I bought it! I understand that many here feel the 10w30 is a better choice. But the 5w30 is what's recommended for all the vehicles in my "fleet," all of which are under warranty. I asked when they usually got it in, and the Tire and Lube manager told me it's a non-replinishable item. Apparantly, they have no control over when they'll get it or how much. This certainly cleared up my confusion over why they seem to stock it randomly.