Fit is basically a mild hybrid, it has a smaller electric motor so it cannot accelerate or start from stop on electric motor alone. the electric motor work in tandom with the internal combustion engine to keep it in optimum efficiency range. so in regular day to day driving the rpm hardly ever go beyond 2k mark, and that's how it achieves good fuel efficiency.
about the oil, I changed it to 5w-40 right after buying the car, and yes, the recommended is 0w, I will go for it in the next oil change.
and it always start the moment you turn the key, it doesn't crank like a regular petrol engine, you just turn the key, and it just starts revving.