The BMW 320d EfficientDynamics Edition, to give its full name, will be officially launched at the Frankfurt Motor Show in September, with the German carmaker claiming that it is the most efficient car in its range at the moment, taking over the mantle from its smaller 316d sibling.

BMW claims that the 320d EfficientDynamics uses only 4.1 litres of diesel per 100km. For a comparison, the Honda Insight hybrid, which is a smaller car, uses 4.4 litres of petrol per 100km.

The 320d EfficientDynamics is powered by a 2.0 litre four-cylinder turbocharged diesel that develops 163bhp, and 360Nm of torque. This enables it to go from 0-100km/h in 9.6 seconds, on to a top speed of 220km/h.

The EfficientDynamics version of the car comes with numerous changes over the standard 3-Series, in a bid to maximise efficiency. Among the changes are a longer final drive ratio for the five-speed gearbox, a longer rear axle transmission ratio, lowered suspension and the use of specially designed aerodynamic alloy wheels with Michelin EnergySaver tyres.

The engine itself has also been modified, with an aluminium crankcase, a diesel particulate filter, common rail direct fuel injection with piezo-injectors and variable intake geometry among the modifications.

The car also comes with a dual mass flywheel with springs between the two parts to help smooth out any engine vibration through the drivetrain as well as new centrifugal pendulum absorbers to further improve smoothness.

Other EfficientDynamics features are also included, such as Brake Energy Regeneration, the Auto Start Stop function, a shift indicator and electronic power steering that only operates when needed. The tyres were manufactured to provide minimum rolling resistance and the suspension has been lowered. The coefficient drag (Cd) figure is now 0.26.

BMW has not neglected luxuries though, with dual-zone air conditioning, parking sensors, BMW's "Professional" radio/CD, a leather-wrapped multifunction steering wheel and Extended lighting, as well as 17-inch alloy wheels, all expected as standard equipment.