From the article:
And since the hybrid system automatically reverts to EV mode any time there is minimal power demand – such as when travelling on level roads under 50 km/h, under light acceleration, while descending slight grades, and while cruising – there is really no need to engage EV mode.
This is incorrect and reveals lack of experience with hybrids.
If you are anticipating descending a long steep hill where you'll need to use the brakes, it's good to be able to deplete the hybrid battery first. That's because you can scrub off more speed on the descent by generating power to refill the battery (to be used later), and at the same time reduce wear on the mechanical brakes.
Similarly, hybrids typically run the engine on cold startups for some time just to warm up the engine, catalytic converter etc. This uses quite a bit of gas, most of which is not needed for propulsion. So, if you can deplete the hybrid battery by using ev mode before ending the previous use, a larger portion of this otherwise wasted running and gas will be used to recharge the hybrid battery.
For people who know how they operate, some ability to force ev mode is beneficial.
EV mode allows the Prius c to be driven for about a kilometre on electric power alone below 40 km/h
Is that all? The Ford Escape Hybrid, with presumably older technology, can go 1-2km at 50-60kph in ev mode. What the article could have stated is that a lot of city running is done at these low speeds, and if one checks the mileage readout, they get much better mileage in that situation than even the already-impressive official numbers. For instance, if you can find a place to do it, driving an Escape Hybrid at 55kph on a flat road means having the gas engine off most of the time, and getting mileage in the mid-50's mpg. The engine just starts up now and then to run at an efficient rpm to recharge the battery.
Like other hybrids, the Prius c has an automatic stop/start system that shuts off the gas engine while waiting at stop lights and restarts it when the brake pedal is released.
Interesting that the Escape Hybrid does not start up the engine when the brake pedal is released. It stays in ev mode until it senses you want more power than ev mode can provide. If you just need to creep in stop-and-go traffic, the engine will stay off. I'd think the Prius should operate the same way. If you give it the usual amount of throttle off the line, the engine will start up in about half a second.
if CR testers did fewer or shorter stops, the automatic stop/start system wouldn’t turn off the engine as often and more fuel would be used.
Probably the CR tests got poor city mileage, not because of the stop/start system, but because every time a hybrid sits and cools off, it has to run the gas engine again on startup just to warm up the engine, catalytic converter etc. That's why some hybrid owners doing many short trips separated by cooling off periods find they get lousy mileage in winter. There's potential to get even worse mileage than equivalent non-hybrids. But the upside is that the cat converter is doing its job on the hybrid more than on the non-hybrids, so the exhaust is typically cleaner.
