See also:

Remove attached partsfollowing use
Remove auxiliary mirrors, roof or rear luggage racks which are no longer required following use. Attached parts on the vehicle impair the aerodynamics and increase the fuel consumption. ...

The concept
The automatic engine start-stop function helps save fuel. The system switches off the engine during a stop, e. g., in a traffic congestion or at traffic lights. The ignition remains switched on. ...

Aerodynamic optimisation of underside panelling
As the excellent drag coefficient (cd = 0.26) would suggest, the aerodynamics of the new BMW 3-Series have been intensively honed in a state-of-the-art wind tunnel. The optimised aerodynamics also ...