If you do the early thing, it only takes 3 hours.
The parking garage opens at 8am. 15 minute walk to the front gate of IOA. They usually open at 08:45am during the summer.
You take a lap around the park going clockwise doing the rides in order. You'll get walkon rides and be back to the front of the park at noon.
By this time, it will be hot, and it's your decision if you wanna eat lunch, hang out, and do more rides. Don't arrive at 11am, the crowds are huge at this time. Do the early thing and you'll enjoy your visit much more.