Even more tangential: Kia declined to cover an engine failure, under warranty that was extended by recall because I change my own oil.

Kia's engines are known to fail predictably even within first 100K miles. They extended their warranty because of it. But then they weasel out of it unless you hire an attorney and go to war.

This would be a violation of the Magnuson-Moss Warranty act of 1975 which requires they show the work done directly caused the failure.

If this were a widespread policy I bet class action lawyers would be all over it without you having to pay for it.

Maybe they researched customers’ backgrounds and only screwed the ones they thought wouldn’t lawyer up

This doesn't require research. Just reject by default and concede if a lawyer shows up. It doesn't cost any money to have a default denial policy and saves millions.

Same case goes to the same court too many times and you are gonna raise eyebrows.