I'm not quite sure about the exact purpose of this topic (where is the "flabbergasted" icon on this forum again?).
The Jazz's e:HEV drive train does - under all driving conditions - what it esteems best for fuel economy.
We have absolutely no influence over this pre-programmed behaviour (as there is no gear shift)!
The only factor we truly can influence is the speed at which we want the car to climb that hill! (and of course: The more power you demand from the car, the higher the ICE's revs become to ascertain the generator provides the electric current necessary to fulfil your right foot's demands)
My "advice": Drive safely, let the car do it's thing and enjoy the ride!
