It's whatever it says in your owners manual. Try reading it again. Carefully, because you void your warranty if you don't follow it.
Right on the money, Joel. I asked a Hyundai technician friend of mine if a transmission claim could be denied on the basis that I have a trailer hitch installed on my SF but never changed the tranny fluid on the "severe" schedule. He just laughed, and said if there's a problem during the warranty period Hyundai will fix it.In the unlikely event you needed to produce documentation supporting regular oil changes, all you'd need to show is they took place every 7500mi/6mo or less. I go sort of middle ground and do oil changes every 5-6Kmi on my 2008 2.7L. w/ synthetic blend 5w20 and Hyundai oil filters.