If you use SAVE, be sure that it engages parallel mode. My do not and keeps the vehicle in series mode which is a waste.
The driver has no direct control over which mode is in use, it's decided by the car's electronics. Parallel mode uses a direct drive from the engine to the front wheels, and so is only available at sufficiently high speeds (so that the engine isn't under-revving), typically ~45mph/70kph. At most speeds (below ~75mph/120kph*) maximum power is via series mode (as the revs at which parallel mode forces the engine to run don't correspond to maximum power output), so if you floor the throttle the car will go into series mode.
You can demonstrate this (where road conditions are safe to do so, like joining a relatively empty motorway) by flooring the throttle from stationary - the car will remain in parallel mode up to ~75mph. With more gentle use of the accelerator, the car will select parallel mode as soon as it's available (~45mph).
I haven't experimented to see if the use of Save/Charge changes this description, but I don't see why it should.
* these numbers could be slightly different for the newer models with the 2.3l engine, but I think the principle is unchanged