At turtle speeds, you won't get more mileage, as the car will also be in lower gears. This is the condition we face in bumper to bumper traffic. Since yours is an automatic, you can try going at economy speeds (on the higher side though), in which the Cruze will just shift at the top gear. Maintain that speed with constant throttle input for some time, the MID FE will surely rise.
In my Dzire MT, the FE shown on the MID goes from as low as 7kmpl (2nd gear, 80kmph) to 30kmpl (5th gear, 40kmph). So, it basically depends on the speeds you are doing. Driving with minimal throttle input at highest possible gear brings more FE.
OT: Lakhvir brother is also getting some great FE from 1.6.
Regards,
Nikunj