The Mercedes-Benz W126 is the company's internal designation for its second generation S-Class, manufactured in sedan/saloon (1979–1991) and coupé (1981–1990) models, succeeding the company's W116 range. Mercedes introduced the 2-door C126 coupé model, marketed as the SEC, in September 1981. This generation was the first S-Class to have separate chassis codes for standard and long wheelbases (W126 and V126) and for coupé (C126). The long 12-year production (1979–1991) resulted in 818,063 sedans/saloons and 74,060 coupés being built, totalling 892,123. W126 is so far the most successful and the longest in production for S-Class. History After the debut of W116 S-Class in 1972, Mercedes-Benz began preparing for the next generation S-Class in October 1973. The project, code-named "Project W126", aimed to provide an improved ride, better handling, and improved fuel efficiency. The oil crisis of 1973 and increasingly stringent emission and safety regulations in the United States had an important influence in developing the W126 for reduced emission and increased fuel efficiency. The W126 design team, led by Mercedes-Benz's chief designer Bruno Sacco, aimed to design a more aerodynamic shape and retain the unmistakable S-Class design elements. The aerodynamic drag was reduced through lengthy wind tunnel testing and reshaping of front end and bumper along with hiding the wipers underneath the hood/bonnet for smoother flow. Reducing the weight was accomplished by extensive use of high-strength low-alloy (HSLA) sheet and polyurethane deformable material for bumpers and side claddings. The lighter alloy material was used for the heavily revised M116/M117 V8 engines for the reduced weight. Both had contributed to the reduction of fuel consumption by 10% as compared to its predecessor. After six years of development, the W126 was introduced at the IAA Frankfurt in September 1979. At the introduction, S-Class was available in two wheelbase lengths (standard and long) and three petrol engine options with one six-cylinder inline engine and two V8 engines. The diesel engine option was introduced in September 1981 exclusively for the North American market. At the 1981 IAA Frankfurt, a coupé version of S-Class, C126, was introduced with 380 SEC and 500 SEC. It was the first time that a coupé version was derived from S-Class chassis. At the same time, the "Energiekonzept" (Energy Concept) was introduced to improve the fuel efficiency of S-Class through engine revisions. The W126 was revised in 1985 for 1986 model year. The revised "Second Series" model range was introduced at 1985