Walmart oil is fine even for 5K, 6K, and 7K interval.
I have used all kinds of oil in my E39: $2 standard dino, Castrol standard, Castrol Synthetic, Walmart Supertech, Costco etc.
The bottom line: there is no difference at all.
Engine smooth as silk.
Time to move on rather than discussing oil. We don't need another oil thread.