What is it that actually triggers the ECO light to turn ON ? Yes I know it means that I'm driving in an efficient economical manner. But here's the thing,...I've seen it light up at 75mph on long straight stretches. At other times, traffic or road conditions do not permit my transmission to shift up into the next higher gear, and yet ECO is on. Lifting my foot off the pedal will turn it on, but accelerating will keep it off until speed is reached. My little 3.7 doesn't deactivate like the hemi's. So if it's not tied to rpms, nor pedal pressure, and evidently not mpg either, what does it work with? Does my computer figure this out somehow ? (no I don't have a fancy EVIC display). It is however an effective tool and I can keep it lit most of the time. Worst mileage I've ever calculated was about 16 and best just a tad over 20.