Mercedes-Benz doesn't go small when it comes to the Frankfurt motor show. This year, the German automaker pulled the wraps off five new models: the C-Class Coupe and S-Class Cabriolet in two flavours each, and this work of modern art, the Concept IAA.

Looking like a globule of mercury, the S-Class-sized IAA — a name that doesn’t actually stand for Internationale Automobil-Ausstellung (the Frankfurt show's official name), but rather for ‘Intelligent Aerodynamic Automobile’ — showcases Mercedes' present obsession with wind-cheating. It's a shape-shifting four-door coupe in the idiom of Mercedes' present CLS-Class.

Below 50mph, the car is merely a handsome executive express. Above that speed, however, it changes shape, hunkering and elongating for maximum aero-efficiency. An eight-part segmented rear-end fairing extends, augmenting the car's length by more than 15 inches. Up front, a fin in the bumper retracts to improve under-body airflow and flaps deploy to more efficiently direct air around the fascia and front wheel arches. And perhaps most amazing, the IAA's active wheel rims flatten, changing their cupping from 2 inches to zero.

Naturally, the IAA is stuffed to its glass roof with advanced technology and high style, including a dazzling four-place passenger compartment with glass instrumentation and cool blue ambient lighting. The car — which features an array of sensors and modules to enable autonomous operation — makes use of a gasoline-electric hybrid powertrain that produces an ample 275 horsepower, enough to enable a 155-mph top speed.

The only dubious aspect of the Concept IAA is Mercedes' claim that its 0.19 coefficient of drag is a "world-record breaker." Make no mistake, a 0.19Cd is extraordinary, but among concept cars — even four-door concepts like the IAA — we've seen better. In the 1980s, for example, Ford built a succession of ever-more-slippery design studies called Probe, the most impressive of which was Probe IV from 1983, a four-door with a drag coefficient of just 0.152 — "the same as an F-16 fighter jet," read the press release.

But the Concept IAA may have one thing the amazing Probe IV sadly lacked: momentum. Mercedes already builds some of the world's slipperiest cars, and the company is eager to hang onto those bragging rights. The carmaker's aerodynamics experts developed some 300 versions of the Concept IAA, and used close to a million CPU hours to simulate airflow. That investment of time and effort, says Mercedes, "is roughly equivalent to that required to develop a production model."

Wouldn't it be a shame to see all that work go to waste?

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