Hello there I have been using 87 octane from the get go, now have approx. 92600 miles and my mileage has varied best being 28 mpg on freeway cruse control set to 75-80 mph best mileage 27.8-28 little variance...
My experience exactly.
There is no benefit to using higher octane fuel when you are not using maximum performance of the engine.
I guess a lot of owners are drag racing between every traffic light..