The Probe III was a concept car developed by Ford of Europe's design team, part of a series of five Probe show cars produced by Ford worldwide to explore aerodynamic efficiency and fuel savings. Unlike the other Probe concepts, which originated in the United States, the Probe III was attributed to Ford's design operation in Cologne. It was unveiled to the public at the Frankfurt IAA motor show in 1981, presented as a fully practical four-passenger car that retained the roominess, comfort and luggage space expected of a family car despite its experimental features.
The car used a semifastback body with five doors and five seats, and was fitted with a 1593 cc four-cylinder engine producing 70 PS at 5300 rpm driving the rear wheels. Ford stated at the time that the average drag coefficient of European mid-size cars with large boots stood at 0.44, and that the Probe III had halved this figure to reach a final Cw value of 0.22, roughly 50 percent better than the rating of ordinary new cars of the period. Ford president Donald E. Petersen said this could offer around 27 percent better fuel economy than a comparable 1982 model.
Ford documented the reduction in drag as a sequence of engineering phases. The first established the basic semifastback shape with covered rear wheels, a rounded and lowered front end with minimal air intakes sized only for engine cooling, flush-fitted lights, and recessed wipers, giving a Cw of 0.34. The second phase involved bonding the front screen flush into the roof rail and shaping the door and window surrounds so airflow would not separate, lowering the value to 0.33. The third phase reduced the front wheel cutouts to minimal dimensions, used flush-fitting tires and wheel covers, rubber wheelarch linings, and brake ventilation ducted from the wheel cover rims, together with special low-rolling-resistance Uniroyal tires in 145/70 SR 15 size run at 2.5 bar, requiring reworked suspension and dampers; this brought the Cw to 0.32.
The fourth phase reshaped the lower body sides near the wheelarches into a teardrop profile, pulling the flanks inward beneath the doors before widening again toward the rear wheelarches, reducing drag to 0.31. The fifth phase introduced a twin-deck rear spoiler mounted between the rear screen and the boot lid, allowing air from the roof and sides to pass beneath it; Ford applied for a patent on this design, which produced downforce and an effect described as forward thrust, cutting the Cw by 0.02 to 0.29. Ford's aerodynamicists noted that a single-element spoiler would have achieved only half the effect. The sixth phase reshaped the door mirrors to shed shorter, weaker air vortices, halving their drag contribution compared with conventional mirrors and bringing the Cw to 0.28; this feature was also patented.
The seventh phase added a patented Venturi skirt, a movable underbody panel beneath the front that could be lowered to enlarge the air inlet and create a ground effect. An electric motor closed it automatically below 40 km/h to prevent damage on ramps or curbs, with a thermostatic mechanism allowing it to open if steep ramps were driven at low speed; this phase alone cut drag from 0.28 to 0.25. The eighth and final phase covered the underbody, divided into five zones, refined through wind-tunnel testing in conjunction with engine air routing, brake cooling, exhaust routing and transmission and driveshaft temperature control, also reducing noise; this brought the finished Cw to 0.22.
Ford published comparative fuel consumption figures contrasting a Cw of 0.44 against 0.22 for both a 70 PS petrol engine and a 50 PS diesel engine, showing notable savings at 90 km/h, 120 km/h and top speed, along with higher attainable top speeds in each case. The Probe III served as the direct forerunner of the Ford Sierra, launched at the same Frankfurt show a year later in autumn 1982, which showed clear stylistic similarities but achieved a production Cw of 0.32, closer to the Probe III than to the outgoing Taunus. The Sierra dropped the concept's extensive electronic instrument display, with the interior forming the greatest difference between the two. The later Sierra XR4i coupe-styled sport variant carried a version of the Probe III's twin-deck rear spoiler.
