In September 1979 a new generation of the S-Class was presented at the Frankfurt International Motor Show IAA. The range of series 126 first comprised seven models. There was a choice of four engines – from the 2.8-liter six-cylinder carburettor engine with 156 hp to the 5.0-liter all-aluminium V8-engine with petrol injection and 240 hp. Furthermore, one could decide between two body variants. Beside the normal version there was a prolonged variant as had been offered for generations in the upper-class saloons. This time the enlargement of the wheelbase with 140 mm was more remarkable than usual. As always it all was of benefit to the passenger leg room and the entrance width of the rear doors.
Important goals in the development of this new series were next to a higher driving comfort and safety the reduction of energy consumption. Using weight reduced materials and a less air resistant body, optimised in the wind tunnel, helped the new S-Class to reduce its fuel consumption by 10 % in comparison to its preceding models. The two eight-cylinder engines of the previous series were replaced by two redesigned units with enlarged displacement and all-aluminium block. The 5.0-liter engine which took the place of the 4.5-liter grey cast iron aggregate was already known from the 450 SLC 5.0. The 3.8-liter all-aluminium engine had been developed after the example of the 5-liter engine from the time tested 3.5-liter V8 with grey cast iron block. Due to their higher power with reduced weight the new V8-engines made a better driving performance combined with a more economic fuel consumption possible. The carburettor and injection version of the 2.8-liter six-cylinder aggregate remained unchanged in the program.