OK, so this thread started in early June and I was intrigued.
This past April, I drove 2,600 miles on a trip from Minnesota down through Iowa, Missouri, Arkansas, Tennessee, Kentucky, Mississippi and back again using regular octane fuel (87). With a strong headwind for the initial portion of the trip, I average only 22.5 mpg. On the way back it was mainly around 26 mpg but eventually climbed up to around 28 mpg as it became less and less windy. Temps were cooler (40 - 80 F), humidity not very high and speeds generally 70-75.
On June 9th I left for another long trip and decided to see if premium gas (93 octane) would make any difference in how my CX-5 ran and/or mpg. On this trip I drove 3,640 miles, starting in Minnesota but mainly driving in Kentucky, West Virginia and Tennessee, returning 3 days ago (20th). The weather for the most part was quite warm (90 - 95 F), higher humidity, significant winds in many areas, many large hills and speeds were usually 70 - 80 mph. I was pleasantly surprised that, given what seemed to be tougher driving conditions, my mpg's were consistently in the 28+ range and eventually approached 30 mpg on one tankful. In additional, my CX-5 just drove "better", a term I use because it is a seat-of-the-pants observation that comes from knowing my vehicle quite well after 36k miles.
With all of the above said, there was certainly no financial benefit to using premium fuel and, in fact, it was rather financially non-beneficial! So while it was a worthwhile experiment for me, I will stick with just regular fuel from now on as the performance using it is perfectly acceptable to me.
Just thought I'd share my real-world experience.