This why I too see it as a hazard; what if it stumbles after you've committed to turning across traffic? A safe turn becomes a pucker moment or worse,

 

This is absolutely true. But how to diagnose it if no faults in system and dealer cannot reproduce it? Really it is happening randomly, sometime I can use the system for a long while and all is correct and sometime I have it twice a day, after that again few days ok, sometime 2-3 weeks and back again. It happening on different Agility settings: ECO, Comfort or Sport and the same issue. Until it will not broke at all giving a faults in system I will have to deal with it the way I am doing now.

 

Sure - in spite of all the engine/system monitoring that Mercedes builds-in for ECO-Start/Stop - a unforeseen "stumble" can be a legitimate concern - especially for those owner's who run less-than-91-premium in their C-Class or in area's like CA and NY where you really/really don't know about the quality of fuel at every station you buy from

Again - the fact is - for anyone who has purchased and installed Vladimir's ECO OBD Frankly - anyone who order's Vladimir's OBD ECO reprograms the ECO the way you want it - turn engine off with ECO Off - and ECO stays off when you restart your MB - and with one button press you can reactivate ECO any time you want it:

https://www.ebay.com/itm/MERCEDES-ca...EAAOSw2iJa-n9S

 

Well I bought my used 2015 C300 in February this year so still learning my car, but mine has not ever stopped and started. I does not work even though the button light is lit up green. I thought it would be a cool feature, but by the sounds of it maybe I should count my lucky stars it doesn't work?

 

It has to be in the right conditions for it to engage.
If it's actively cooling/heating the cabin, engine still warming up, Agility in Sport+, battery too low; can all cause the engine to stay on. Also, if you don't have the brake pedal down far enough when stopped, it won't engage either.

 

My thing is why does it always engage when the light is about to turn green? Lol countless times I get to a red light fully stopped waiting for the eco thing to engage and 80% of the time, it finally engages when is about to turn green ....talk about grinding somebody gears lol

 

Mine sends a signal to the traffic light so that it changes as soon as i push the brake and Hold comes on.