Opel also produced the first mass-production vehicle in Germany with a self-supporting ("unibody") all-steel body, closely following the 1934 Citroën Traction Avant. This was one of the most important innovations in automotive history. They called the car, launched in 1935, the Olympia. With its small weight and aerodynamics came an improvement in both performance and fuel consumption. Opel received a patent on this technology.
The Calibra holds the title of having been the most aerodynamic car in the world at its 1990 launch, with a drag coefficient of just 0.26. With engines ranging in displacement from 1998 cc to 2498 cc, the car reigned supreme over other makes at the time. Its privileged position as the most aerodynamically efficient car would be held until the end of the 90's when the Calibra was overthrown by new Audi and Honda releases, the A2 and Insight respectively.
The Kadett C appeared in August 1973 and was Opel's version of the General Motors' "T-Car". It was the last small Opel to feature rear-wheel drive, and remained in production at Opel's Bochum plant until July 1979, by which time Opel had produced 1,701,076. Of these, 52% had been exported outside West Germany, most of them to markets in other parts of western Europe.
In 1957 Opel Product Director Karl Stief was mandated by General Motors headquarters in Detroit to develop "the perfect Anti-Volkswagen" ("einen perfekten Anti-VW"). The development team was headed up by Stief, supported by Hans Mersheimer (car-body) and Werner K. Strobel (engine and running gear), under conditions of such secrecy that even now very little is known of the development history of the 1962 Kadett. It has been alleged that GM was trying to conceal a new technique of platform and design sharing between Opel and its British sister company Vauxhall, which released the strikingly similar Viva HA in 1963, a year after Opel introduced the Kadett. Over the subsequent two decades Opel and Vauxhall's ranges would rapidly converge as Vauxhall's design independence from Opel was eroded to the point where by 1985, Vauxhall's car range entirely consisted of rebadged Opel models.
The Kadett clearly featurt a muckle mair modren design than the Volkswagen Beetle which then dominatit the mercat for smaw family caurs in Germany an various surroondin kintras. The Kadett affered mair passenger space, massively mair luggage space an a muckle less encumbered view oot. Its watter cooled ingine enabled it tae provide a far mair effective heater. Even fuel consumption wis unner maist conditions superior tae that o the Volkswagen, an mony commentators muckle preferred the Opel's handlin an its licht an effective brakes tae those o the mercat leader.
A convertible version wis an aa available, for the first time in 1987, biggit bi Bertone o Torino/Italy, bringin it tae line wi key competitors sic as the Ford Escort an Volkswagen Golf which wur available as cabrios afore. For the 1988 model, capacities wur raised tae 1400, 1800 an a new 2000 cc ingine, again uised on the GSi an Vauxhall Astra GTE. In 1988, a 16-valve twin-cam version wis developed for a hie performance GSi/GTE model, yieldin 156 hp (115 kW) in manufactured form.