Nothing specific. I don't know about the Eco mode so
I looked it up. Apparently it just de-sensitizes the accelerator pedal. In my Metro, the Eco light trains you to short shift up through the gears.
I never got to the factory rated mileage, how do you compare? Generally the three areas of opportunity are powertrain, aerodynamics and the 'nut behind the wheel'. The first two come pre-optimized, but with aero there are some opportunities that come with their own costs. Wheel spats and skirts, trailer hitch cargo box, etcetera.