Well most part it comes from a lower emission and Higher MPG rating, so it will reduce it's carbon footprint.
They have eco tech technology in their motors and an eco mode that the ecu is programed and help the motor reduce this and that, and change shift point and etc to help optimize fuel economy.
As for the GMC for production they try to have cars share same Platforms, such as the Terrain is equal to the Nox, and the Cruze = to the Verano. Helps cut cost be Redesigning a car based on the same frame.
Also its what you define as "eco - Friendly"