I only have 800km on mine so far so I'm hoping mileage improves but right now my MDS will not come on over 90km/hr, so it is never active at highway speed. I do not have an eco light, but it is definitely noticeable when it activates at low speeds.
I can be disabled by putting your truck in 6th gear. It will shift normal from stops and everything. Works for mine. You just have to put in in 6th every time you shift from drive. I cant stand MDS. I have a muffler delete and it drives me crazy between 40 and 75mph. I usually drive with it off. Dont notice any mpg difference. I live in Texas and its decently flat ground.
I think I get better mileage with the MDS off using the switch manually method, it seems like I am able to keep the truck in a better range myself, plus it doesent lag between the MDS switching on and off. I'm coming from a 2013 V6 with the 8speed, I wish they would have given us a Eco light on the 6.4
ECO Light must not have been on the 2014s my 2015 has it but it rarely comes on unless I'm driving under 90km/h. Only 400km so hopefully it will improve as it breaks in. I'm only getting 11MPG or 21L/100km with mixed driving so far.
My 2014 does not have the eco light either. Wouldn't matter much though because I disabled the MDS with the Diablosport Trinity tuner. Actually haven't seen much difference in gas mileage.
Actually got slightly better gas mileage with the MDS turned off on my 2011 Sport.
I've got a 2015 Sport with 5.7. 3.21 gears. 1100 miles.
I had to turn on my ECO indicator in the settings..
I notice it comes on quite a bit and I can actually drive and accelerate gradually with it in ECO. I was pleasantly surprised how often and long it stays on. I've even ECO'd up gradual hills on the highway maintaining speed. My Avalanche would drop out as soon as I breathed on the gas pedal.
MPG is improving with break-in. I'm seeing low-mid 20's cruising around town and backroads. But that's relaxed driving.
I also find it's better to accelerate up to speed fairly quickly since you're sucking gas anyways, then just cruise from there.