German engineers develop 'green' Porsche

Porsches are known for the sound of their rippling horsepower under the bonnet, but the company’s new petrol-saving hybrid actually has the motor off or running on batteries more than half the time – leaving the driver with little more than the sound of the wheels on the road.

Using a system developed with Volkswagen and Audi engineers, the prototype Cayenne S Hybrid relies on a combination of petrol, electric power – and coasting – to boost mileage from 14 mpg in the city to 24 mpg while reducing C02 emissions.