The S-Class was officially introduced for 1991 as the W140 series. With the introduction of the S-Class, Mercedes-Benz combined several cars into one class, resulting in a wide variety of models for this generation.
Overall, the car became larger and more aggressive in appearance. A new grille, headlights and completely new rear design were added. The interior also received a major facelift. The door panels and dashboard were completely redesigned while the center-console only received a rather minor facelift.
The car also featured double-pane window glazing that substantially reduced outside noise from intruding into the cabin while, at the same time, adding to the car's substantial heft. For details like this, the W140 is often known as the last Mercedes to be "overengineered", a Mercedes trait that was costing the company in product delays and overbudgeting.
Once again, a large SEC was available, and in 1992 a V12 engine joined the lineup for the first time with the 600 SEL. In 1994 all Mercedes model names were rationalized, with the SE/SEL/SEC cars becoming the S-Class. The alphanumerical designations were inverted, for example the 500 SE model becoming the S 500, while SEL models became S 500 Long and SEC coupés adopted the CL designation, although they were still part of the S family. Production of W140 models lasted through 1999.
The W220 S-Class began production in 1999, lasting until 2005. New features included Airmatic air suspension, COMAND (Cockpit Management and Data System), and Active Ventilated seats, which use miniature fans in the seats to move air through perforations in the upholstery to cool the passengers’ backs. The exterior was completely redesigned. The angular lines of the 1990's S-class were replaced with a more rounded and aerodynamic design, giving the car a sportier appearance. The interior was also completely revamped with new the door panels, center console, dashboard and seats. The V12-equipped cars feature a cylinder deactivation system called Active Cylinder Control.
The introduction of the W220 saw the departure of the large coupés to their own line, the C215 CL-Class. The models produced include the S 280, S 320 (which was later replaced by the S 350), S 430, S 500, and S 600, the latter featuring a 500 PS (368 kW/493 hp) V12 engine. The two AMG models also produced are the S 55 and S65 AMG, the latter featuring the twin-turbo V12 engine producing 612 PS (450 kW/604 hp). The extremely rare, V12-powered S 63 AMG was produced in 2001 only. An undisclosed number were sold exclusively through AMG in European and Asian markets.
The W220 S-Class was replaced by an all-new W221 model in the autumn of 2005, with export to other markets beginning in 2006. The W221 was introduced to the North American market at the 2006 North American International Auto Show in January.
It is slightly larger than its predecessor, and it features a more luxurious, Maybach-like appearance, as well as three newly developed engines with up to 26 percent power increase. The interior is also completely new, all materials have been upgraded and the center-mounted transmission has been replaced with a column-shifter.
The 7G-TRONIC seven-speed automatic transmission is standard, except on V12 engines, where the 5-speed Sequentronic is maintained. 4MATIC four wheel drive will become available at a date to be determined. One major mechanical change is the elimination of brake by wire technology in favor of conventional hydraulic power assist. The brakes continue to become more advanced, however, with the new Brake Assist Plus system monitoring for an impending collision and increasing braking if needed, while the Distronic Plus cruise control can now bring the car to a complete stop.
| Years | Trim levels | Engine type | Displacement | Power | Fuel |
|---|---|---|---|---|---|
| 2006–present | S 320 CDI | Turbo Diesel V6 | 3.0 L | 231 PS (228 hp/170 kW) | Diesel |
| 2006–present | S 350 | V6 | 3.5 L | 272 PS (268 hp/200 kW) | Gasoline |
| 2006–present | S 550 | V8 | 5.5 L | 388 PS (383 hp/285 kW) | Gasoline |
| 2006–present | S 420 CDI | Turbo Diesel V8 | 4.0 L | 314 PS (310 hp/231 kW) | Diesel |
| 2006–present | S 600 | Twin-turbo V12 | 5.5 L | 517 PS (510 hp/380 kW) | Gasoline |
| 2006–present | S 63 AMG | V8 | 6.2 L | 510 PS (503 hp/375 kW) | Gasoline |
| 2006–present | S 65 AMG | Twin-turbo V12 | 6.0 L | 612 PS (604 hp/450 kW) | Gasoline |
Road accident statistics on a model-by-model basis from the UK Department of Transport show that the Mercedes-Benz S-Class is one of the safest cars on the UK roads (measured in terms of chance of death in an accident) —between three times safer than the safest Volvo and BMW 7-Series models and only matched by the Jaguar XJ series and Land Rover.
The S-class was the Australian Wheels magazine's Car of the Year for 1981 and again in 1999.