There are 3 Walmarts in Cedar Rapids, their Mobil 1 inventories are hugely different. One stocks every oil type in every jug size, another has a very limited stock, 5W30 and 10W30 only.
Individual store managers must have a huge latitude in what they stock.
Today, I could find everything EXCEPT 0W20 in 5 qt jugs, perhaps with Toyota's prodding this will become more available.