Is there any way to make the ECO mode the default mode? I don't see it in the manual and probably wouldn't use it exclusively but it would be nice to know if it were possible.

 

As far as I know it is not possible.

 

That's what I figured. We also have a Camry Hybrid where the ECO mode doesn't change unless you actually press the button so if it was on when the car is turned off, it's on when the car is restarted.
About the only reason I can think of to use it on the Volvo is to take advantage of the lack of engine braking on highway trips.