Battery Efficiency [[ 2 engines]] -- G6 Performance

​A question please,

the G6 Performance has 2 engines, however , in order to accomplish good battery efficiency, if we put ON the ECO mode (and driving 100km/h in the highway) will the front engine turn off to save battery???

Any similar scenario where one engine that is not required is turned off??

Or always the 2 engines are on draining battery? Thanks you so much

Thanks!!