Data logging regular vs. premium

Last evening I did a fill up of 91 E0 for the 4th tank in a row in the Maverick Hybrid. My results were the best yet. 2/3 city 1/3 hiway in the 55-70 mph range. 49.4 MPG. It was a 1/2 tank short fill due to upcoming trip. The fillup was at the same pump, set on low flow to first click. 23¢ added to get to nearest quarter dollar amount.


Do I think premium helps. Yes, but I think the E0 is most of my approx 12% gain in mileage. Yes, I haven't had my coffee yet. Maybe constant use of premium is slowly reprogramming the ECU for better efficiency, or a dozen other possibilities that exist. Just presenting my 2¢ worth of verified results of switching to higher octane.
Fuels used were Costco 87 and Costco 93. These would be calculated as R+M/2, not RON or MON.

The 87 and 89 on the logs is manifold vacuum as measured by the MAP sensor in kPa.
Thanks! Sorry for the confusion. I couldn't find the octanes used in the text unless I just missed it.
I use 91 premium ethanol free in both the Sonata 2.4L DI and the 2.4L Forte non DI.

Both vehicles will surpass the EPA rated miles on highway and city. Sonata will will cruse at around 37 mpg on highway at 60 and the Forte 6mt over 39 mpg at 60 in 6th.

Low end torque is noticeably more responsive as in less throttle is needed for acceleration also wot pulls way harder on 91 E-0 vs E10 87 on the H/K 2.4L

City mileage on both H/K is mid to higher 20's on average.

Average for both 2.4l's is over 30 mpg in day to day.

After owning these 2.4 L for many years now I really believe they were tuned to run 91 plus premium and then de-tune to run 87.

87 makes the 2.4L "sluggish"

This is purely first hand experience on a H/K 2.4L and not all engines will respond the same way.
Thanks for the info, I may have to try this next summer when we tow our camper. I don't have a data logger but could see if the mpgs change in the Expedition.