I think I'm on record on another thread saying I favor 87 except for perhaps towing situations. I just got back from a couple weeks of about 1600 miles in which I went the whole trip on 92 octane just to see what the diff.
I don't know if it was the more moderate temps on the trip versus home (live in desert), or the increased octane, but I loved the seemingly increased response & power that was _significantly felt_ on the 92 octane.
I gassed-up at Cosco's along the way, and the Premium price was the same or lower than what we pay for Regular here locally without a Cosco... hence I could rationalize the experiment.
Mileage on the trip varied from 14.249 MPG hotrodding around Sacto area in stop & go traffic to a high of 26.209 MPG from Bakersfield to Sacramento on Hwy. 99. Average for the entire trip was 21.53 MPG on Premium. The highest previously achieved on Regular via Hwy. driving is around 22-23 MPG, so maybe a bit better MPG can be had on Premium, but I see no difference in City driving (MPG wise).
Air was on the whole time except for some driving in Sacto area. Hwy. speed usually around 80-85, ...did get tired of messing around with a kid in a Toyota on I-5 coming back down south, and did hit 105 MPH briefly. Also hit a bird on I-40 at 85 MPH, terrible noise/windshield held... but don't think that affected MPG for me as bad as it did for that poor bird. :-(
Anyway, back at home with the higher prices currently around $1.60 for Regular and $1.80 for Premium... I'm going back to Regular! (...until my next outing [smile])