The P4 was developed from Opel's earlier "Laubfrosch." Conventional in both styling and engineering, it was well constructed and reliable, and popular for those reasons. The first opel Kadett was a minor sensation, both technically and in terms of price. More than 100,000 of these four-seater models were built from 1936 to 1940 in Rüsselsheim, which even then was one of the most advanced Car-making plants in europe.
"This new car is an important innovation and valuable addition to the small car class," wrote the Opel press department in December 1936. By small car, Opel meant the 1.0-1.5 liter class. The "valuable addition" that created a minor sensation was the cost: The first Kadett with its revolutionary unitary body construction available as sedan or convertible cost only 2,100 reichmarks. The speedy four-seater could do nearly 100 km/h and it did not take long to find its way into the hearts of the general public.
It also found favor with the press: "As the first test drives have confirmed, the Kadett is certainly not an ordinary vehicle in this price range," wrote a German newspaper, "Braunschweiger Tageszeitung," on December 5, 1936. The chassis with Dubonnet independent front suspension and leaf-spring rear axle stemmed from the Opel Olympia, and the L-head four-cylinder gray cast-iron engine was taken from the Opel P4.
It generated 23 hp from a capacity of 1,073 cc. the advantages of taking the engineering from a modular system also played a key part in the low price of the car. Like its big brother the Olympia, which it also resembles, the Kadett was a snazzy car. It was characterized by harmonious proportions with fastback and integrated headlamps. In 1938 a major mid-cycle enhancement added a new radiator mask in late art deco style - experts today count this model as an intermediate generation. The trunk was accessible from inside and the spare wheel was mounted outside on the trunk. The engineering used in the Kadett was certainly up with the times:
The Kadett had a notably comfortable drive on its perforated and thus relatively lightweight steel wheels and 4.50x16 low-pressure balloon tires. Its engine even then featured a downdraft carburetor with a venturi tube. Power was transferred to the rear wheels via a dry single-disk clutch and a three-speed transmission. braking was performed hydraulically via four drums. much attention was given to the corrosion protection system used for the Kadett. The steel shell was coated inside and out, including all the hollow profiles.