https://www.cars.com/articles/2009/0...rolet-equinox/
GM program engineering manager Doug Smith... Eco mode locks up the Equinox’s torque converter at lower speeds — most automatics do this at highway speeds — and changes shift patterns in the four-cylinder’s six-speed auto. It cuts the engine’s speed at idle, too, but it doesn’t affect the accelerator pedal. The net effect? About 1 mpg...
We leave the eco button on all the time in my wife's equinox. my parents have one too and my dad calls his the "make it feel like a 4 cyl" button