The Mercedes-Benz S 400d 4MATIC, produced from 2017 to 2020 as part of the W222 S-Class facelift, represented a significant offering in the luxury sedan segment. This variant utilized a powerful diesel engine paired with a sophisticated automatic transmission and all-wheel drive, positioning itself as a compelling alternative to gasoline-powered S-Class models and competitors like the BMW 7 Series and Audi A8. It was a mid-to-upper trim level, offering a blend of performance, efficiency, and luxury features. The W222 generation S-Class, launched in 2013, was a technological showcase for Mercedes-Benz, and the 2017 facelift further refined its design and capabilities.
Powertrain & Engine Architecture
The heart of the S 400d 4MATIC is the OM 656.929, a 2.9-liter inline-six cylinder diesel engine. This engine marked a departure from the previous V6 diesel configurations used by Mercedes-Benz, offering improved efficiency and refinement. The OM 656 features a steel piston design, a stepped combustion process, and a two-stage turbocharging system. The two-stage turbocharging utilizes a small turbocharger for immediate response at low engine speeds, supplemented by a larger turbocharger for increased power at higher RPMs. This configuration helps to minimize turbo lag and deliver a broad torque curve.
Fuel is delivered via a commonrail direct injection system operating at extremely high pressures (2,700 bar), ensuring precise fuel atomization and efficient combustion. The engine also incorporates a diesel particulate filter (DPF) to reduce emissions, meeting stringent Euro 6 standards. The engine produces 340 horsepower at 3,600-4,400 rpm and a substantial 700 Nm (516.29 lb-ft) of torque between 1,200-3,200 rpm. The compression ratio is a high 15.5:1, contributing to the engine’s thermal efficiency.
The “G-TRONIC” 9G-TRONIC automatic transmission is a nine-speed automatic gearbox designed to maximize fuel efficiency and provide smooth gear changes. It features a wide gear ratio spread, allowing the engine to operate within its optimal efficiency range more frequently. The transmission is electronically controlled and offers multiple driving modes, including Comfort, Sport, and Manual, allowing the driver to tailor the driving experience to their preferences. The 4MATIC all-wheel-drive system distributes power between the front and rear axles as needed, enhancing traction and stability in various driving conditions.
Driving Characteristics
The S 400d 4MATIC delivers a refined and powerful driving experience. The high torque output of the diesel engine provides effortless acceleration, with a 0-62 mph (0-100 km/h) time of 5.2 seconds. The 9G-TRONIC transmission contributes to smooth and seamless gear changes, enhancing comfort during both city driving and highway cruising. Compared to the S 500 (gasoline V8), the S 400d offers comparable acceleration but with significantly improved fuel economy. While not as overtly sporty as the AMG-tuned S-Class models, the S 400d provides ample power for confident overtaking and merging. The all-wheel-drive system inspires confidence in inclement weather, providing enhanced grip and stability. The gear ratios are tuned for a balance between acceleration and fuel efficiency, with a relatively tall final drive ratio to reduce engine RPM at highway speeds.
Equipment & Trim Levels
The S 400d 4MATIC typically came well-equipped with standard features befitting a flagship luxury sedan. Standard amenities included leather upholstery, heated and ventilated front seats with massage functions, a premium sound system, a large infotainment display with navigation, and a comprehensive suite of driver-assistance systems. These systems often included adaptive cruise control, lane-keeping assist, automatic emergency braking, and a 360-degree camera system. The interior featured high-quality materials and meticulous craftsmanship, creating a luxurious and comfortable cabin environment.
Optional extras included features such as a panoramic sunroof, upgraded leather options, rear-seat entertainment systems, and advanced driver-assistance packages. The S 400d could also be equipped with Mercedes-Benz’s AIRMATIC suspension, which provided an exceptionally smooth and comfortable ride by automatically adjusting the suspension damping based on road conditions. The dashboard configuration was consistent with other W222 S-Class models, featuring a dual-screen display for the instrument cluster and infotainment system.
Chassis & Braking
The S 400d 4MATIC utilized an independent multi-link suspension system at both the front and rear axles. This suspension design provided a comfortable ride and precise handling. The AIRMATIC suspension, when equipped, further enhanced ride quality by continuously adjusting the damping characteristics of the shock absorbers. The vehicle’s weight (approximately 1985 kg or 4376.18 lbs) was managed effectively by the suspension system, minimizing body roll and providing a stable driving experience.
Braking duties were handled by ventilated disc brakes at all four corners. The braking system was equipped with ABS (Anti-lock Braking System), Electronic Stability Program (ESP), and other advanced safety features. The electric power steering provided precise and responsive steering feel. Tire size was typically 245/50 R18, mounted on 18-inch alloy wheels.
Market Reception & Comparison
The S 400d 4MATIC was generally well-received by automotive critics. It was praised for its powerful and efficient diesel engine, smooth transmission, luxurious interior, and advanced technology. The diesel engine offered a compelling alternative to the gasoline-powered S 500, providing similar performance with significantly better fuel economy. Fuel consumption figures ranged from 5.6-5.7 l/100 km (42-41.3 US mpg) combined, and CO2 emissions were between 147-150 g/km. Compared to the S 350d, the S 400d offered a noticeable power increase. Reliability reports generally indicated good reliability, although diesel particulate filter maintenance was a consideration for owners.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | S-Class |
| Generation | S-Class (W222, facelift 2017) |
| Type | S 400d 4MATIC G-TRONIC |
| Start of Production | 2017 |
| End of Production | 2020 |
| Engine | 2.9L Inline-6 Diesel |
| Engine Code | OM 656.929 |
| Power | 340 hp @ 3600-4400 rpm |
| Torque | 700 Nm (516.29 lb-ft) @ 1200-3200 rpm |
| Transmission | 9-speed Automatic (9G-TRONIC) |
| Drivetrain | All-Wheel Drive (4MATIC) |
| 0-62 mph | 5.2 seconds |
| Top Speed | 250 km/h (155.34 mph) |
| Fuel Consumption (Combined) | 5.6-5.7 l/100 km (42-41.3 US mpg) |
| CO2 Emissions | 147-150 g/km |
| Kerb Weight | 1985 kg (4376.18 lbs) |
| Fuel Tank Capacity | 70 l (18.49 US gal) |
| Trunk Space | 510 l (18.01 cu. ft.) |
Legacy
The S 400d 4MATIC represents a significant step in Mercedes-Benz’s diesel engine technology. The OM 656 engine proved to be a robust and efficient powerplant, and the 9G-TRONIC transmission further enhanced its appeal. On the used car market, these models are generally sought after for their blend of luxury, performance, and fuel economy. While diesel engines have faced increased scrutiny in recent years, the S 400d 4MATIC remains a desirable option for buyers seeking a refined and capable luxury sedan. Regular maintenance, particularly concerning the diesel particulate filter, is crucial for long-term reliability. The W222 S-Class, including the S 400d 4MATIC, is remembered as a benchmark for automotive technology and luxury.
