Every car I've ever owned, I've done the experiment and compared $/mile (dollars per mile, not per gallon) on premium and regular. Every one of my cars has had

Every car I've ever owned, I've done the experiment and compared $/mile (dollars per mile, not per gallon) on premium and regular. Every one of my cars has had a noticeably lower cost per mile on premium compared to regular (I'd love to quote the number but it's been around 10 years since I ran the rest on my current car so all I recall is the outcome). I've encouraged several friends and family members to run the same experiment, and all reported the same result. Significantly newer cars with octane sensors might change this result, but I suspect it holds for most of the used cars on the market out there, so for at least some of us the more "expensive" gas is actually the cheaper gas.