Which again leads to why? As alluded to, best 'speculation' I got, since Hyun/Kia spec for many vehicles and their aftermarket OF warnings, AZ STP decided to stay away.
So Hyun/KIA encourage consumers to use only OEM oil filters? Who is their OEM supplier?
Interesting you mention Hyundai. A couple days ago I saw a Hyundai SUV. Not sure what model. It looked newer as in probably not older than two or three years max. As it drove down the street a plume of white smoke emitted as though the piston rings were completely shot. I thought how could a vehicle this new be neglected that quick? Or could it be quality issues?