The Opel tree frog was a car that was sold from the Rüsselsheim manufacturer in the period between 1924 and 1931 with the subtitle " car for everyone". In addition, the Opel tree frog was the first vehicle that has been manufactured in Germany in assembly line production. The name Opel tree frog is then developed from the vernacular, because the vehicle has been delivered as standard with green paint, the original model name was derived from the manufacturer of the engine (Opel 4 PS). Opel was equipped tree frog with a 1.0-liter engine accelerated the vehicle to a top speed of 60 km / hr. During the production period, the Opel tree frog learned various modifications that affected the PS numbers of the engine especially. So the last Opel tree frog vehicles were delivered with 20 hp. During the construction period could, thanks to the rapid production of the automobile almost 120,000 units manufactured by Opel tree frog was replaced in 1931 by the Opel P4.