I'm having the same issue with my 2013 TI FWD, I've filled up twice so far with just over 650 miles on it with the DTE down to 5 miles and both times I was only able to get around 13.5 gallons in the tank and the gauge reads full. I contacted the dealer and they are looking into it. Does anyone have any updates if they got any answers from their dealers??
Other than that the car is awesome!!!