I believe that the modes just change the throttle response, flooring it should give you the same amount of power in eco, normal, or power. Besides the difference in the way AC works, a good driver could probably get the same mileage in eco or normal mode.
I don't have an EV button in mine (yet), but it looks like you have until the engine kicks on after you first power it up to go into EV mode. After the engine turns on, you have to wait until its warmed up to use EV mode again.
|