1999-2002 Mercedes-Benz S-class (W220) S 400 CDI V8 (250 Hp) 5G-TRONIC

The Mercedes-Benz S 400 CDI V8, produced between 1999 and 2002, was a variant of the W220 generation S-Class. This model represented a significant offering in the luxury sedan segment, combining a powerful diesel engine with Mercedes’ renowned comfort and technology. It occupied a middle ground within the W220 lineup, positioned above the naturally aspirated V6 models (S320) but below the higher-performance S500 and S600 variants. The S 400 CDI was designed to appeal to buyers seeking a blend of performance, fuel efficiency, and long-distance cruising capability.

S 400 CDI: A Diesel Flagship

The S 400 CDI distinguished itself from other W220 models through its advanced diesel powerplant. While the S-Class was traditionally associated with gasoline engines, Mercedes-Benz recognized the growing demand for efficient, high-torque diesel options, particularly in European markets. The “CDI” designation signified the implementation of Common-Rail Direct Injection technology, a significant advancement in diesel engine refinement and performance. This variant aimed to provide a sophisticated diesel experience, minimizing the traditional drawbacks of noise and vibration while maximizing power and fuel economy.

Powertrain & Engine Architecture

At the heart of the S 400 CDI lay the OM 628 DE 40 LA engine, a 4.0-liter V8 diesel. This engine, with its code 628.960, produced 250 horsepower at 4000 rpm and a substantial 560 Nm (413.03 lb-ft) of torque between 1700 and 2600 rpm. The engine featured a robust cast iron block and aluminum cylinder heads. The Common Rail Direct Injection system, supplied by Bosch, delivered fuel at extremely high pressure directly into the combustion chamber, optimizing combustion efficiency and reducing emissions. The engine also incorporated a bi-turbocharger system with an intercooler, further enhancing power output and responsiveness. The V8 configuration contributed to smooth operation and a refined driving experience.

The S 400 CDI was exclusively paired with Mercedes-Benz’s 5G-TRONIC automatic transmission, a five-speed unit known for its smooth shifting and adaptive learning capabilities. This transmission was designed to work seamlessly with the engine’s torque curve, providing effortless acceleration and comfortable cruising. The transmission offered selectable driving modes, allowing the driver to prioritize either fuel economy or performance.

Driving Characteristics

The S 400 CDI offered a distinctly different driving experience compared to its gasoline-powered siblings. The abundant low-end torque of the diesel engine provided effortless acceleration in everyday driving situations. While not as overtly sporty as the S500, the S 400 CDI could achieve 0-60 mph in approximately 7.4 seconds and reach a governed top speed of 155 mph (250 km/h). The 5G-TRONIC transmission contributed to a relaxed and refined driving experience, with smooth gear changes and minimal shift shock. The gear ratios were optimized for both highway cruising and city driving, providing a balance between fuel efficiency and performance. Compared to the S320, the S 400 CDI offered significantly more power and torque, resulting in a more confident and capable driving experience. However, it lacked the outright acceleration of the S500 and S600.

Equipment & Trim Levels

As a flagship sedan, the S 400 CDI came standard with a comprehensive array of luxury features. Standard equipment typically included leather upholstery, power-adjustable heated front seats with memory function, automatic climate control, a premium sound system, and a multi-function steering wheel. Safety features were also extensive, including ABS brakes, traction control, stability control, and multiple airbags. Optional extras included a navigation system, rear seat entertainment, massaging seats, and various wood and trim options. The interior design was characterized by its elegant and understated luxury, with high-quality materials and meticulous attention to detail. Trim levels were generally differentiated by the availability of optional packages and cosmetic enhancements.

Chassis & Braking

The W220 S-Class featured a fully independent suspension system, providing a comfortable and controlled ride. The S 400 CDI utilized a sophisticated suspension setup designed to isolate occupants from road imperfections. Front suspension consisted of a five-link design, while the rear employed a multi-link setup. The braking system consisted of ventilated disc brakes at all four corners, providing ample stopping power. Anti-lock brakes (ABS) and Electronic Stability Program (ESP) were standard features, enhancing safety and control. The S 400 CDI typically featured a hydraulic power steering system, offering precise and responsive steering feel. The vehicle’s weight (approximately 4178 lbs / 1895 kg) was managed effectively by the suspension and braking systems, contributing to a stable and confident driving experience.

Market Reception & Comparison

The S 400 CDI was generally well-received by automotive critics, who praised its powerful engine, smooth transmission, and luxurious interior. The diesel engine’s fuel efficiency was a significant selling point, particularly in Europe where diesel fuel was less expensive than gasoline. However, some critics noted that the diesel engine was slightly noisier than the gasoline engines offered in the S-Class. Compared to the S320, the S 400 CDI offered a substantial performance upgrade without sacrificing fuel economy. Compared to the S500, it provided a more economical alternative, albeit with slightly less power. Reliability was generally good, although the complex Common Rail injection system required careful maintenance. The S 400 CDI’s fuel economy figures were approximately 24.5 US mpg combined, and CO2 emissions were rated at 253 g/km.

Technical Specifications

Legacy

The S 400 CDI represented a pivotal moment in Mercedes-Benz’s diesel strategy, demonstrating the potential for high-performance, refined diesel engines in the luxury segment. While the W220 S-Class has been superseded by newer generations, the S 400 CDI remains a sought-after model among enthusiasts. The OM 628 engine is known for its durability and longevity, provided it receives regular maintenance. On the used car market, well-maintained examples of the S 400 CDI can command premium prices, reflecting their rarity and unique combination of performance, luxury, and fuel efficiency. However, potential buyers should be aware of the potential maintenance costs associated with the Common Rail injection system and other complex components. The S 400 CDI stands as a testament to Mercedes-Benz’s engineering prowess and its commitment to providing a luxurious and sophisticated driving experience.