The leading car manufacturers continue to make some of their most popular vehicles more fuel efficient in a bid to attract a new batch of eco-conscious consumers.

Now Audi has introduced its fuel consumption optimised version of the A4 mid-size saloon car, the A4 2.0l TDIe. It consumes an average of 4.6litres of diesel per 100 kilometres and emits just 120g/km of carbon dioxide (CO2).

The vehicle adopts the 100kW 2.0litre TDI engine that was first seen in the A6 TDIe. The turbo-charged diesel features high pressure common rail injection as well as an energy recuperation system and stop/start technology. There are also further fuel savings that come from grille and under-body modifications which enhance the aerodynamics.

The start-stop system cuts the engine power at idle when the clutch pedal is released and the gear level is in neutral. It then restarts in two-tenths of a second when the clutch is depressed – much more rapidly than most comparable systems. It is estimated that this reduces CO2 by around 5g/km, although it can also be deactivated at the tough of a button.

The recuperation technology offers further savings by recycling a proportion of the wasted kinetic energy generated under normal braking and storing it temporarily in the vehicle battery to reduce the engine load when the car accelerates again.

Its peak power is 4,200rpm and 320Nm torque. It reaches 62mph in 9.5 seconds and has a top speed of 143mph.