eco is a version of a Cruze. It's either a eco version or it is not......nothing to turn on or off.
The eco had several mileage enhancements such as air shutters built into the lower grill and a slightly different front air splitter.
Manual trans versions had different gearing.
All eco's had low rolling resistance tires that were fairly effective if run at the elevated pressure they were capable of (51psi max).
Most eco owners picked up on a fair mileage loss with the installation of conventional tires.
You haven't mentioned your driving environment so if the car is being operated in a cold climate (here in Chicago, -6f at this writing) small engines are at a great mileage disadvantage due to drag from lubricants and wheel bearings.....something a larger, higher torque engine shrugs off.
Naturally, extended warmup time (0 mpg) and fuel trims being much richer, longer, drive mileage in the toilet as well.
What is your actual (computed with a calculator, not dashboard readout) fuel mileage?