The owners manual and gas filler door on my 2007 3.0 V6 Montereo assembled in Bogotß, Colombia states 91 octane or higher is required. There are only two grades here and premium is more than a dollar higher than regular at about four dollars a gallon. The dealer salesgirl no doubt to make the sale, told us it?s fine to use regular and it?s true I haven?t heard any pinging going up our long mountain road while using that grade. I?m guessing the kaka will hit the fan when it?s time to take it in for the annual emissions test. Can anyone think of any other reason why this nearly twenty year old engine design (G12 is it?) would require premium gas?