Just bought a 2010 Prius IV and loving the car. Minor annoyance, but wondering why it's so difficult to get the car to enter or stay in EV mode. When I'm able to get into EV mode, it often beeps that it's leaving EV mode due to excessive speed, but I'm often doing barely 10 mph when this happens. I was under the impression that I could do up to 25 mph. Yesterday, I was floating at 8 mph and it said that was excessive speed. More often, though, I can't even get into EV mode. It says "EV mode currently unavailable" and I have no idea why. Doesn't matter if I'm not moving or if I'm driving slowly.
Long story short, the emission system is not warmed up yet. There are countless threads on this topic, but that's all you really get to know. If you want detail, get an aftermarket gauge and watch coolant temperature for the engine.
Temperature and battery's SOC will affect whether you could get into EV mode and at what point you get kicked out of it. My suggestion is that you don't use EV mode except for a couple of situations. For me, about the only time I use it is when I'm entering a busy parking lot or trying to leave.
Don't worry - The Prius can only use EV mode in vary limited situations. You will get you best MPG by letting the car decide when to use EV. Remember that the car is smarter than you are.
I've found EV mode to be useful moving around in a parking lot but otherwise, not worth the effort. If you want some EV time, there are better options. Good luck! Bob Wilson
Suggest starting with the manual. The "EV" light on the power meter comes on when the ICE shuts off. Watch this and learn when it happens, and how to "encourage" it.
Leave the car in "ECO" or normal mode. The car will decide based on how hard you press the accelerator.
