So, it my understanding that the Japanese version of the Gen II Prius' came equipped with an ECO mode button that uses only the battery on speeds below 34 mph. Can anyone comment on how much of an increase in MPG this mode gives the Japanese version?
It is nice to have the button if you are backing out of the garage to stop in the driveway. Or, you don't want neighbors to know you are home... Or, if you like to sneak up on people and startle them! But, for mileage it is not a big help. Using pure EV and draining the battery all the time will cost you more in the long run.
EV mode is really a waste as all the power ultimately comes from gasoline or regeneration. There is no such thing as a free lunch, and it applies to the Prius as well. The power ultimately comes from the ICE burning gasoline which recharges the battery. When in EV mode, you are strictly running off of the battery which runs it down. Then the ICE comes on and recharges the battery. As Eclipse pointed out, in the long run you actually end up with lower overall MPG if you try to run EV mode than just driving the Prius normally. If you are trying to increase your MPG, you should learn how to hypermile. There are links in my signature that discusses that. Best of luck to you and welcome to Prius Chat.
You don't say where you are In the us there's an aftermarket kit available I have one, haven't used it in years
I installed the EV switch in my 2008. I only engage EV mode when I know I will be going down a big hill and the battery will be over full before getting all the way down. That way I save some gas on the approach and then get the batteries completely topped off (all green bars) going down the hill. I usually exit EV mode after the hill since the car generally knows what to do better than I do.
