Tierr@_de_N@die: If a PHEV car allows you to choose the driving mode and one of this modes is full electric then it is up to the driver to do it in the right way. In terms of performance no doubts that the hybrid mode will be a lot more exciting but the client has at least the choice of decreasing its emissions.
A parallel hybrid system is an entirely different kettle of fish. It fires up every time the car encounters a hill, accelerates away from a stoplight, or needs to pass another vehicle. The engine is connected to the wheels mechanically, which means its is used much more frequently than the engine in a series hybrid. It’s a question of priorities, really. A series hybrid is an electric car first and a gasoline powered car second. A parallel hybrid is a gasoline powered car that gets an occasional boost from a battery and an electric motor. Technically, both are plug-in hybrids but they are world’s apart when it comes to how they operate.
Source (cleantechnica.com): Transport & Environment Calls Out PHEV Manufacturers For Higher Than Advertised Emissions