I totally believe the eco light is for the MDS. I have been testing mine and when i shut off the MDS with the gear limiter as mentioned above, I no longer get the eco light ever. I could always make the eco come on but with the MDS off i cant even if i try. So that makes me believe that the eco is in direct correlation with MDS. Plus i could always slightly feel it kicking into MDS, dont feel that with the gear limiter on.I usually don’t either, but, if you get on a flat road and set the cruise to 43 or 44, it’s right at the on/off point and I can definitely tell when it goes in and out, and the feel/sound is directly related to the “eco” light on the dash. Many people say the eco doesn’t equal MDS, I call bull crap based on my experience they are directly correlated.