I've already posted my disgust and rage with my Tucson's fuel economy in another thread... but i still feel there is something different going on mechanically when "eco" is enabled/disabled.
I notice a difference even just cruising at 50km/h... when eco is enabled...the rpms are definitely reduced. When just giving it easy gas under acceleration the actually groans at low rps (under 2000rpms) However when eco is disabled the car comes to life and the transmission is more responsive. It will not be so delayed in downshifting to get more torque. I'm not convinced it's just an "eco light" to show where the ideal driving is for fuel economy.
maybe it's completely psychological... or is it possible this is all semantics and they've re' branding this whole ECO thing with an improved "active-eco" on new models?
This guy explains the new active eco system