[RedDevil]

The hybrid system is useful for situations where it can help avoid using the brakes or run the ICE at a very inefficient load level. It also helps acceleration, of course.

In situations where you can keep a constant load by varying the speed, like when negotiating a small hill on the highway, that is preferrable to drawing from the battery on the ascent and filling it back up descending, as the losses in the movement->electricity->battery->electricity->movement conversion are substantial.

Nowadays I try to coast on level load, e.g. not drawing and not storing.
When driving slow the electric mode will kick in by itself. I then go P&G varying the speed (if not hindering traffic) rather than maintaining speed drawing power. If I do the latter at some point the ICE will kick in and recharge the battery, but the FE while it does that is worse than when gently accelerating in the P phase.

It is great to have the hybrid system when you can put it to good use, but it is even better to avoid using it if that is possible too.