Eco: mode or gimmick?

I know what you’re thinking. That’s a rather odd bunch of vehicles to be in the same story considering they have nothing in common. That would be true except, there is one feature they all have " a small button that activates a driving mode called, Eco mode! There are nearly 40 cars sold in the Indian market that offer this feature, and that got us curious. Does this actually make a difference to the efficiency, or is it just another one of those overused automotive jargons like “cockpit inspired interior”. So we took four cars,...