I don't follow your logic. You're worrying about the wrong thing. Say you have an engine issue, but your engine looks spotless on the inside for using HPL. I'm sure Toyota won't say "you took all precautions and took care of your engine, used a lubricant which provided more MOFT, but we'll deny your warranty because it's politically incorrect to use 0W-30 over 0W-20." If they want to deny a warranty, they will deny it even if you did every oil change with the Budweisser equivalent of motor oil at the dealership, and if they want to help you because they value your business, they will use common sense and honor your warranty. You should quit IFOW, and instead enjoy your vehicle and use the oil you think will get you the most life out of it.