Purchased a leftover 2013 on 4/24/15 and have put nearly 10,000 miles on her since then. Have to say that I am very happy with the mpg I am getting. I use an app called Road Trip to track my expenses/mileage and and this is how it breaks down for me.

Premium 93 Octane - 7,857 miles 44.60 mpg
Premium 91 Octane - 159 miles 44.98 mpg
Regular 87 Octane - 64 miles 38.42 mpg
91 Ethanol free - 1,735 miles 46.08 mpg

Mileage is better with the ethanol free gas but when you factor in price differential between the ethanol free gas and the 93 Octane, the 93 Octane is the better bang for the buck. Also, my mileage took a bit of a hit when I replaced the stock windshield with a larger one from clearview shields. I lost between 1.5-2 mpg with the larger shield. But the trade off in comfort was well worth it.