I use 91 octane from either Shell, Costco or Quick Trip, and Yes the car does require it. It's on page 225 of the Owners manual. When I refill my range is 325 to 350 for a weeks worth of driving, and I refill once per week on Friday after the work week.
When I drove from Phoenix to Tucson, about 120 miles, I averaged 36 mpg while in non-Sport mode and no paddle shifters. When driving in mixed conditions I can usually get about 24 mpg. That being said, I drive it like I stole it with the paddle shifters, and Sport+ selected, and even then I still manage to get 21 mpg.
Not too bad as my 2011 V6 Camaro was getting me about 18 when I would drive it like in the above scenario. On the highway I would get 29 mpg.
Hope that helps.