With a Cd value of 0.23, the CLA sets a new benchmark – both within the Mercedes-Benz model range and among all production vehicles. The drag area, Cd x A – which is crucial to aerodynamic resistance – also leads the field, at 0.51 m². The CLA 180 BlueEFFICIENCY Edition, which is due to hit the streets in June, even manages to better this value with its Cd value of 0.22, and when it comes to the drag area, the four-door coupé crosses a magical line with its 0.49 m2. This makes the CLA-Class more streamlined than any other car.

The good air flow characteristics, which are a major contributory factor to the vehicle's low fuel consumption in everyday conditions, result from numerous aerodynamic optimisation measures. These include a low A-pillar shoulder with adapted A-pillar geometry, aerodynamically optimised exterior mirrors, wheel trim designed for low aerodynamic drag or a specially-developed aero light-alloy wheel and serrated wheel spoilers on the front and rear wheel arches.

The patented wheel spoiler was developed with the help of airflow analysis. This seemingly innocuous component reduces undesirable air turbulence in the wheel arches in no less than three ways, by lowering linear turbulence, deflecting the airflow from the wheels and stabilising shear waves with its serrated edge. The wheel spoiler remains effective whatever the suspension level and wheel dimensions.

Extensive underbody panelling, additional panelling in the middle area of the rear axle and an aerodynamically optimised rear silencer followed by a diffuser improve the flow of air under the underbody.

In addition the new CLA offers the lowest level of wind noise in its segment. Numerous measures contribute to make this possible:

Exterior noise is also minimised by the reduced height of the A-pillar shoulder.

Anti-soiling measures are another aerodynamic discipline – and another area in which aerodynamics specialists at Mercedes-Benz have worked painstakingly on the CLA. Soiling can arise from rain, vehicles travelling ahead and spray thrown up by the vehicle's own wheels. Keeping windows and exterior mirror lenses as clean as possible, and therefore having the best possible visibility under all conditions, makes a contribution to active safety.

In the wind tunnel the aerodynamic specialists optimise components with the help of a fluorescent liquid which makes the soiling clearly visible. The aim is to direct water away so that the side windows and exterior mirror lenses remain clean. This is influenced by the geometry of the A-pillar with its integral components and the geometry of the exterior mirrors and trim strips in the frameless doors.

For example, the side windows: by means of minor geometrical changes of the mirror housings and optimisation in detail, with seals and a special water-capture runnel, soiling has been significantly reduced.