Mercedes-Benz W140

Mercedes-Benz W140 at a glance

How the W140 was developed

Work on the car began in 1981. Design proposals were compared from 1982 to 1986, and on 9 December 1986 the board chose a shape drawn by Olivier Boulay under design director Bruno Sacco. Engineering prototypes ran from early 1987 and the exterior was frozen in September 1987. Sacco named the Jaguar XJ40 and the BMW E32 7 Series as the cars he watched most closely.

The BMW mattered for another reason. When BMW revealed the V12-engined 750i in 1986, Mercedes decided its flagship also needed twelve cylinders, and the launch slipped by about 18 months, from September 1989 to 1991. Pilot production ran from June 1990 to January 1991. The overruns cost chief engineer Wolfgang Peter his job, and the finished car reached showrooms in April 1991, with North American sales from 6 August 1991.

Engines and gearboxes

The engine line-up mixed new four-valve petrol units with variable valve timing and one carried-over diesel. Every petrol engine had a catalytic converter from the start.

The V12 was the first twelve-cylinder engine in a Mercedes passenger car. In Europe it gave 300 kW until 1992; from 1993 it was retuned to 290 kW. By our calculation, a long-wheelbase 600 SEL at up to 2,190 kg carried about 7.3 kg per kW, while an S 280 at 1,890 kg had about 13.3 kg per kW. The 1996 OM606 was the first Mercedes diesel six with four valves per cylinder. AMG also offered an S 500 6.0 with 279 kW, mainly for Japan.

The six-cylinder petrol cars came with a five-speed manual as standard, and a four-speed or, from 1994, five-speed automatic as an option. The V8 and V12 used a four-speed automatic until August 1995 and an electronically controlled five-speed from September 1995. From June 1996 the five-speed automatic was the only gearbox, which makes the W140 the last S-Class sold with a manual. Diesels were automatic only.

Saloon, coupé and Pullman sizes

The long saloon adds 100 mm, all of it for rear legroom. The Pullman of 1995 came as S 500 or S 600, and the S 600 Pullman could be ordered with armour. The old 1cars page quoted a 525-litre boot and a drag coefficient of 0.31; we have not found these in a second source.

Technology the W140 introduced

The car arrived on the threshold of networked electronics: it was the first Mercedes to use a CAN bus, with five control units linked. Many features that later became normal appeared here first or early.

The double glazing kept the cabin quiet but made each door glass heavy. Long-wheelbase cars had four-zone climate control, and orthopaedic seats with inflatable cushions were an option.

Names, facelifts and the CL split

The first cars used the old badges, such as 300 SE or 500 SEL. In June 1993 Mercedes switched to the new naming system: the 500 SEL became the S 500 and the 600 SEL the S 600, with the letter placed first. A facelift shown at Geneva in March 1994 went on sale the following month. A second round of changes, introduced in Europe in June 1996, brought single-colour paint, xenon low beam and clear rear indicator lenses. The coupé, sold first as 500 SEC and 600 SEC, became the S-Class Coupé in 1993 and a separate CL-Class in 1996.

A few one-offs show how far the platform was stretched. In 1997 Mercedes built an S 500 long landaulet for Pope John Paul II, and AMG built estate versions with a 7.3-litre V12 for the Sultan of Brunei.

Price and reception

The W140 was bigger, heavier and up to 25% dearer than the W126, and it arrived during the early-1990s recession, so sales started slowly. Japan's new luxury brands made the gap obvious. In the United States in 1992 a 300 SE cost 71,500 US dollars, against 44,300 for a Lexus LS 400 and 43,600 for an Infiniti Q45. By our calculation, the Mercedes cost about 61% more than the Lexus. Today many enthusiasts call the W140 the "last true S-Class", because its successor, the W220, drew criticism for its engineering and early reliability.

What to check when buying one

A W140 today is a luxury car between 28 and 35 years old, and its condition matters far more than the badge. Points to look at:

• Electric window regulators: the heavy double glass loads them, and failures are common.
• Wiring and electronics: corrosion and ageing control units cause faults, from throttle sensors to cruise control.
• Hydraulic self-levelling and ADS dampers on V8 and V12 cars: check for leaks and a level stance.
• The V12: parts and labour cost far more than on the six- and eight-cylinder cars.
• Rust at the jacking points, wheel arches and boot floor on cars that lived in winter climates.

For daily use, a late S 320 or S 300 Turbodiesel with the five-speed automatic is the simplest choice. The 500 and 600 models suit buyers who want the full experience and can budget for upkeep. You can set the W140 against other big saloons of the period with the power-to-weight calculator or browse the 1990s classics section.

The W140 among its rivals

The BMW 7 Series E23, E32 and E38 page shows the rival the W140 was built to beat, and the Lexus LS guide covers the car that undercut it on price. The comparison tool sets any two models side by side. For the whole family from the W116 to the current model, see the Mercedes-Benz S-Class hub; other models are in the Mercedes-Benz catalogue.