Warranty is not void by using others type of oil(s). You always and will get warranty, except if you tinker with genuine wiring, have an accident where that part is covered in warranty starts malfunctioning, e.g ECU or where it is plain simply your fault.
Warranty claims are stronger if you follow company specifications, since the dealership will send a case to KHI headoffice, where the decision will take place. I personally have only used LM or Caltex oil, still got stuff done from warranty- ( Speakers 3x replaced) and other things which I unfortunately cannot remember.
Warranty issue = marketing gimmick > increase of genuine SGO products sold> Abroad travels for employees.
What I always strive to get from Dealership is the genuine oil filter ( the large one for 950.-), and get the car tuned from there as well.