In the owner's manual it recommend 91 octane gas for my Nissan Murano, so rather than regular or the 89 octane, I've been putting in the 93 (premium), the only one that is 91 or above. Those are the three octane choices offered at local gas stations for me. The car will operate with regular too. For our Ford and Mazda there is no such recommendation of a higher octane gas, so we use regular.
Is the study saying that owners who are following recommendations in their owners manuals are wasting money and that the recommendations car manufacturers are giving are unnecessary / wrong and cause consumers to waste money who are foolish enough to follow theses or is the study saying that people who have cars without that recommendation in their owners manual are wasting money by buying gas that has a higher octane level than what the manufacturer recommends for their car? I am wondering if they are including the first group that would include people like me with that study. And in that case, isn't the real culprit the car manufacturers who are publishing the owner's manual?
I know many people use regular even when the owner's manual recommends something else, as they think following that recommendation is unnecessary, and they may be right. I'm one of those people who not knowing any better does all the regular maintenance and follows other recommendations in that manual as close as possible, thinking that is the best thing for my car. I typically only get a new car every 10 years or so and drive each car I get about 200,000 miles, so want to keep the car in good shape and have it run as trouble free as possible. (I may be wasting money on gas, but my automotive knowledge is so low that I'm not one to follow my own path on maintenance and recommendations. I don't know who to trust on this topic, and just decided to go with what my owners manual recommends.)