Interesting finding today - picked up a couple of Mazda OEM B6Y1-14-302 filters (used on the Miata and other 4 cylinder Mazda blocks) and to my surprise, "Made in Thailand" is stamped on the box.
Checking the box closely, the part number is actually B6Y1-14-302AUS - has anyone else seen this...
Closest aftermarket I've seen to 5w20 is the Castrol Formula R 5w30.
Dave, amen to no one using it - 20W50 is the norm here. I think BITOG regulars would be surpised (shocked?) that 20w50 usually makes up half of the shelf space at auto stores.