The Mercedes-Benz W116 is a series of flagship luxury sedans produced from September 1972^[2] until 1980.^[3] The W116 automobiles were the first Mercedes-Benz models to be officially called S-Class, although some earlier sedan models had already been designated unofficially with the letter 'S' for Sonderklasse (German for 'special class'). The W116 was selected as European Car of the Year in 1974.

The W116's development began in 1966, which was only a year after the launch of the W108/09. This was the first Mercedes-Benz sedan to feature the brand-new corporate styling theme, which endured until 1993, when the 190 was discontinued. The design, finalized in December 1969,^[4] was a dramatic leap forward, with more masculine lines that combined to create an elegant and sporty character. The basic design concept continued the themes originally introduced on the R107 SL-Class roadster, especially the front and rear lights.^[1] As with the SL, the W116 received the ridged lamp covers which kept dirt accumulation at bay; this was to remain a Mercedes-Benz design theme into the 21st century.^[5] The W116 was Friedrich Geiger's last design for Mercedes-Benz; his career had started with the Mercedes-Benz 500K in 1933.

The W116 was presented in September 1972. The model range initially included two versions of the M110 engine (straight-six with 2746 cc displacement) — the 280S (using a Solex carburetor) and the 280SE (using Bosch D-Jetronic injection), plus the 350SE, powered by the M116 engine (V8 with 3499 cc displacement). After the 1973 oil crisis, a long-wheelbase 280SEL was added to the model range.

The larger 4.5-litre M117 V8 engines were developed in response to US emission regulations and initially fitted to the 350SL and 350SLC for the US market in 1972, which were renamed as the 450SL and 450SLC in 1973. Mercedes-Benz introduced the 450SE and 450SEL for both US and international markets in 1973. The 4.5-litre models were available with three-speed automatic gearboxes only, while the models with smaller 3.5-litre V8 engine could be ordered with a four-speed (and later five-speed) manual gearbox. The 450SE and 450SEL received a plusher interior, with velour or leather seats rather than the checkered cloth of the lesser models. The door cards had the velour or leather inserts.^[6]

The 4.5-litre M117 V8 engines had 225 PS (165 kW) in most European and international markets, 190 hp (142 kW) for the US market, and 200 PS (147 kW) for Swedish and Australian markets.^[5] The 450 models received a plusher interior as well, with velour or leather seats rather than the checkered cloth of the lesser models. The door cards were also of a different design, with pads being pulled up around the windows.^[6]

The W116 had independent suspension and disk brakes on all four wheels.

The most notable W116 model was the high-performance, limited-production 450SEL 6.9, which was introduced in 1975. This model boasted the largest engine installed in a post-war Mercedes-Benz (and any non-American production automobile) up to that time,^[7] and it also featured self-leveling hydropneumatic suspension.

Exclusive to the North American and Japanese markets was the 300SD, the world's first passenger car with a turbocharged diesel engine, which was introduced in 1978. No 300SD model was offered in Europe (where diesel engines were well-received and had tax advantages) until 1991, when the W140 300SD was finally introduced in Europe and international markets.

The 450SE was named the European Car of the Year in 1974, even though the W116 range was first introduced at the Paris Motor Show in the fall of 1972.^[8] The W116 became the first production car to use an electronic four-wheel multi-channel anti-lock braking system (ABS) from Bosch as an option from 1978 on.

Production totaled 473,035 units. The W116 was succeeded by the W126 S-Class in 1979. The W116 was sold throughout Europe, the Americas, Asia, the Middle East, Africa, and Australia.

In 1975, the W116 was upgraded with a new fuel injection system to comply with revised exhaust emission standards in European markets. A slight power reduction was a result of this update. In 1978, a series of engine upgrades restored original performance levels with new fuel injection systems. Initially the early models (1973-1974) of the W116 with the Twin Cam inline 6 used the D-Jetronic fuels injection system with computers and MAP sensor that are both prone to failure after more than 20 years of use. From 1975 onward they used the K-Jetronic mechanical fuel injection system, a less complicated system that proved to be much more reliable in the long run and injectors cost 6x less than the D-Jetronic system. The W116 equipped with the K-Jetronic system, used a cast-iron fuel distributor, which can be prone to rust over time if moisture or water is present in the fuel. This was changed to an alloy fuel distributor in the following model W126 and is not subject to corrosion.

W116 was first model from Mercedes-Benz to feature the hydropneumatic suspension system. While the principle is similar to Citroën’s, Mercedes-Benz made some changes. The hydraulic pump was driven by the timing chain instead of a rubber belt for more reliability (Citroën’s system would lead to loss of hydraulic power if belt failed). Mercedes-Benz utilised the hard rubber dampers as temporary dampers in event of hydraulic failure. The height adjustment had a smaller range of height as compared to Citroën (5 cm versus 50 cm). Unlike Citroën, the car did not “sink” to the ground after shutting off the engine, and the driver did not have to wait for the hydraulic power to spool up and lift the car to the operating height.

The full hydropneumatic suspension system was fitted to the 450SEL 6.9 as standard. In 1977, the self-levelling rear suspension system was offered for 450SEL as an extra cost option outside the North American market.

North America was a key market for the W116. The model range for the U.S. market at launch was 280SE, 450SE, and 450SEL. For 1975, 280S was launched as a response to the 1973 oil crisis. The 6.9 was added in 1977 with the MSRP of $38,230 while 280S and 450SE were dropped due to slow sales. 300SD, the world’s first passenger car with turbocharged diesel engine, was launched in the United States and Canada in 1978: the S-Class model with turbocharged diesel engine was exclusive to the North American and Japanese markets until 1991.

^[10] It had a turbocharged 3.0-litre inline-five diesel engine developed from that of the C111 experimental vehicle. It was developed to help Mercedes-Benz keep from falling afoul of the Corporate Average Fuel Economy (CAFE) standards introduced in 1975; it became a best seller and helped considerably raise Mercedes-Benz' average fuel economy.^[10]

Due to the modifications demanded by the U.S. Government, U.S. Models of the Mercedes-Benz W116 were described by journalists as if a "beautiful car was beaten with the malaise ugly stick."^[11]

The high-performance 450SEL 6.9 version of the S-Class was built on its own assembly line by Daimler-Benz in Sindelfingen, Germany and based on the long-wheelbase version of the W116 chassis. The model was generally referred to in the company's literature as the "6.9", to separate it from the regular 450SEL.

The 450SEL 6.9 was first shown to the motoring press at the Geneva Auto Show in 1974 and produced between 1975 and 1981 in extremely limited numbers. It was billed as the flagship of the Mercedes-Benz car line and the successor to Mercedes-Benz's original high-performance sedan, the 300SEL 6.3.

The W116 S-Class incorporated a broad variety of Mercedes-Benz safety innovations.

• Four wheel anti-lock brakes were first featured as an option on the 1978 W116 S-Class. This system prevents the wheels from locking while braking. The system improves steering control during hard braking situations, and to shorten brake distances.
• Strengthened body structure. The W116 featured a more stable security passenger cell with a stiffened roof frame structure. High strength roof and door pillars, along with other reinforced zones, provided enhanced vehicle occupant protection.
• Deformation zones (crumple zones) in the front and rear.
• A padded dashboard, deformable switches and controls, and a four-spoke steering wheel with impact absorber and broad impact cushion aimed to reduce occupant injury during collisions.
• The fuel tank was no longer fitted at the rear end, but was now placed above the rear axle for added protection.
• Wraparound turn signals made it easier to communicate with nearby drivers.