The same trip was driven first with the Yaris Hybrid and then with the Corsa, at the same time of the day in 2 consecutive weekdays.
On this road, with the Yaris Hybrid, I have a personal record of 3.5 L/100km, attained in optimal conditions, in the evening, with no traffic, but the recording I'm going to analyze refers to a less than stellar 4.2 L/100km.
On the same track, the diesel engine scored 5.2 L/100km, with a comfort and a noise far worse than the hybrid car.
I suspect the A/C was preventing the engine from stopping.
This is another notable difference with the hybrid, that doesn't suffer from this limit.
There are some others different behaviors of the engine:
On the diesel car, RPMs of the engine are mostly proportional to the car speed.
On the hybrid car, this is not the case.
In the same chart, the engine load is also present: the hybrid engine always works with an high load.
The diesel engine, especially when decelerating, has a low load.
The average load value for the hybrid is 84.63% versus 53.35% of the diesel.
There's a thread about this on the Hybrid Synergy Forum