The phrase "eco button" refers to a button or switch that helps save energy or reduce environmental impact in a simple and convenient way. Full definition
Without pushing the magic green ECO button on the dash, we averaged 40 MPG overall. (bestride.com)
All manual versions feature Kia's EcoDynamics fuel - saving, CO2 - reducing measures, including Intelligent Stop & Go and aerodynamic drag - reducing measures, while automatics have an Active ECO button which alters the operation of the engine's electronic control unit and the compressor on the climate control system, bringing potential fuel savings of around 9 %. (thekoreancarblog.com)
Conversely, hitting the ill - placed ECO button, partially hidden by the steering wheel, lights up a green ECO indicator in the speedometer and promptly neuters most of the fun, but it jacked the Hyundai's gas mileage up into the low 30s, perfect for trolling down the highway on the way to some twisty bits where drivers can push the Veloster's track - tight, overly - damped suspension. (digitaltrends.com)