I saw this online and not sure if the ST owners are affected but seems like the MPG rating is not accurate on 2014 Fiesta's as well as other models. Ford says that they will send 'good will' checks ranging from $125 to $1050 depending on mileage, purchase date, and etc.
article can be read below.
http://www.freep.com/article/20140612/BUSINESS0102/306120185/Ford-mileage-Fusion-hybrid-C-Max-Lincoln-MKZ-Fiesta-EPA-fuel-economy
article can be read below.
http://www.freep.com/article/20140612/BUSINESS0102/306120185/Ford-mileage-Fusion-hybrid-C-Max-Lincoln-MKZ-Fiesta-EPA-fuel-economy