I don't understand why everyone is so hung up on using the right oil for warranty purposes. If your goal is super long drivetrain health and you feel that the CAFE driven lubrication recommendation is not going to cut it for whatever reason put in whatever you want in the vehicle and don't think about it. You can prepare in advance oil receipts for the proper oil, for the minimum amount of oil changes one way or another and then if you had a warranty claim you would be covered.
Realistically any engine claim in (5 years 60K miles) you have is not going to be caused by an engine oil unless you try using 20W50 in your Prius in Alaska, or run 0w20 in your Coyote Mustang on a Phoenix racetrack for several race events.
Obviously if you have a claim or even roadside failure, I would put in the right oil grade, just to be safe before getting the vehicle to them. They don't know what was in your car prior to bringing it in and will not do forensic level analysis to try to fight you if everything in the engine looks clean as a whistle. Its more likely going to be a repair for a known issue, at which point they won't question anything at all, once you provide the minimum amount of receipts.