I have my Gen 4 since May and overall I am happy like pooh bear with a jug of honey. However, I am observing some interesting things on the new fancy display. 1. The current fuel consumption bar stays at zero while the engine is idling. 2. But the MPG (for us up here North l/100km) calculation includes the fuel used while idling. So the fuel consumption results are OK - as accurate as they are. Now it is winter here in Canada and the 'little engine that could' runs quite a bit more than during the summer. It will staRT after an few seconds of "READY" to heat whatever needs to be heated to comply with the air pollution standards. And heated seat or not, it is needed to warm my tootsies (and hands). As a direct result it is impossible to achieve summer mileage. Short trips are a real killer - lol
If, for instance it is 5 deg (C) outside and you have the Climate Control set at 25C, it will start the engine immediately in the morning - assuming that you want it to warm YOU up - which is probably what you want. If you don't want the engine to start immediately on a more mild (say 15C) morning, if you turn the temp to "LO", then it won't try to get the heater going, and will use EV for a little longer. You might have to do that the night before, as it'll sense the temperature almost immediately.
Naturally, as the bar shows you miles per gallon. At idle when you're stopped, you are getting zero miles per gallon. Naturally, because your fuel economy results will be calculated as total miles (kilometers) traveled divided by number of gallons (liters) consumed. It doesn't show you only rolling fuel economy. If you want to stop consuming fuel at idle, turn the power off when you'd otherwise be idling. Yup, that's about right. With my 2014 Prius v, I get about 46 mpg in the summer and 40 in the winter. It's a combination of "winter blend" gasoline which has less energy per unit, and having to run the engine more to generate the heat necessary to heat the cabin.
Fuel consumption units in Canada are topsy-turvy: display is in "Liter per 100 kilometers". Showing zero when stopped with the engine running is contradictory; it should in fact show infinite, or 99, or whatever. But it is what it is.