From the linked article, Hyundai had this statement on their website, which FTC didn't like and I agree with them:
Quote:
“The use of Hyundai Genuine Parts is required to keep your Hyundai manufacturer’s warranties and any extended warranties intact.”
It's pretty clear to me what is says and there is no reason to believe that Hyundai didn't use this for denying some warranty claims, otherwise they would not have put it there, despite individual experience.
I even remember reading posts here mentioning the use of Hyundai oil filter to keep the warranty intact.