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 have benefits for noise reduction and roadholding. In particular, streamlined design of the underside plays a big part in minimising lift forces. The BMW 3-Series' aerodynamically optimised underside - with extended streamlined panels at the sides, under the engine compartment shield and at the front part of the exhaust tunnel - provides unprecedented standards of sealing. Additional aerodynamic covers, which create a diffusor effect at the rear axle, further reduce drag and lift forces, while at the same time improving stone chip protection. Also, the front aprons are designed to create an "air curtain" effect which reduces turbulence in the wheel arch area - again reducing drag. The aerodynamically designed wheel arches, and the air deflectors in front of them, likewise help to reduce fuel consumption.