Finally, fifth gear, the carbon value: plug-in cars will only be as green as the electricity they're using.

BBC: Promise, but daunting challenges for electric cars

It is also a regular location for television shows such as Top Gear and Fifth Gear and featured in the James Bond film, Casino Royale.

BBC: Tracks

But they may have to shift into fifth or at least fourth gear instead of the usual second gear of the Chinese government.

FORBES: China Official Warns Of Tough Months Ahead For Exporters