ecco qua....
https://en.wikipedia.org/wiki/Chevrolet_Volt
General Motors has avoided the use of the term "hybrid" when describing its
Voltec designs, even after the carmaker revealed that in some cases the combustion engine provided some assist at high speeds or to improve performance. This contribution from the gas engine is only at high speeds. Normal driving there is no contribution and the car runs all electric
...e anche....
https://en.wikipedia.org/wiki/GM_Voltec_powertrain
The general layout of the initial production platform is considered by some to be a plug-in
series hybrid design (since mechanical power initially drives the generator, which in turn charges the battery pack), despite its transmission design that makes it, by definition, a
parallel hybrid. Power is drained from the batteries to run the electrical motors which move the vehicle. The internal combustion engine can run at a constant speed for both optimal efficiency and mechanical simplicity (i.e., there is no need for variable cam phasing). The Voltec, like the Prius, uses a planetary gearset to couple power from two sources to the wheels. Unlike the Prius, the Voltec only rarely drives the wheels with mechanical assist from the engine, and only when battery charge is depleted.
[1][2][9] The Voltec could therefore be considered a
power-split hybrid.