My CX-50 Premium Plus is just the opposite. I am real happy with the mileage mine has shown. I've only had it 2 weeks and have less than 400 miles on it. We live abut 70 miles southeast of Nashville in a small town, it hasn't had any real city driving. A week ago we drove it down to Huntsville, AL and my wife drove it back. We filled it up for the first time on the way back, and when we got home it was showing 32.5 MPG. My wife was driving about 60 MPH on state highways on the way home, although we did do a little real city driving also. Now I've got about 150 miles on the tank and it's showing 29.4 MPG. I probably should tell you that I'm 73 years old and my wife's 70, so there hasn't been much full throttle driving. One way that I've noticed that helps the mileage. If you keep your foot on the gas and hit the brakes to slow down, a lot of energy is dissipated as heat. In the CX-50, If you let off the gas, after some normal coasting, you'll feel the car slowing quicker. I think they turn the fuel injectors completely off, because you can see the tach drop down when it starts slowing harder. This has to save a lot of gas.
Also check the accuracy of the MPG indication. FIll it up, and reset the MPG display. Run the tank low and fill it again and calculate your actual MPG and compare it to the display. Obviously I haven't checked mine yet, but Wednesday we're going into Nashville and we'll fill it up on the way home and I'll see how accurate mine is.