The Mercedes-Benz S-Class (W221) S 320 CDI 4MATIC, produced from 2006 to 2009, represented a compelling blend of luxury, performance, and efficiency within the flagship S-Class range. Positioned as a mid-range offering, it slotted between the gasoline-powered S 350 and the higher-performance S 500 models. This variant combined a potent diesel engine with Mercedes’ 4MATIC all-wheel-drive system and the advanced 7G-TRONIC automatic transmission, appealing to buyers seeking a refined grand touring experience with reduced fuel consumption. The W221 generation S-Class, launched in 2005, introduced significant technological advancements and a redesigned interior, solidifying the S-Class’s reputation as a benchmark for automotive innovation.
Powertrain & Engine Architecture
The heart of the S 320 CDI 4MATIC is the OM 642.930 3.0-liter V6 diesel engine. This engine is a longitudinally mounted, turbocharged common rail diesel, representing a significant evolution in Mercedes-Benz’s diesel technology. The OM642 engine family is known for its robust construction and relatively high output for its displacement. Key features include a cast iron block, aluminum cylinder heads, and four valves per cylinder (DOHC). The turbocharger, coupled with an intercooler, provides increased air density for improved combustion and power delivery.
The common rail direct injection system, operating at a pressure of 1600 bar, precisely meters fuel into the cylinders, optimizing combustion efficiency and reducing emissions. The engine produces 235 horsepower at 3600 rpm and a substantial 540 Nm (398.28 lb-ft) of torque at just 1600 rpm. This high torque output, available at low engine speeds, is a hallmark of diesel engines and contributes to the S 320 CDI’s effortless acceleration and relaxed cruising ability.
Paired with the engine is the 7G-TRONIC automatic transmission, a seven-speed unit that was a significant advancement over previous Mercedes-Benz automatic transmissions. The 7G-TRONIC utilizes a torque converter and planetary gearsets to provide smooth and efficient gear changes. It features a wide gear ratio spread, allowing for both strong acceleration and optimized fuel economy. The transmission also incorporates a manual shift mode, allowing the driver to select gears for more spirited driving. The 4MATIC all-wheel-drive system distributes power to all four wheels, enhancing traction and stability, particularly in adverse weather conditions.
Driving Characteristics
The S 320 CDI 4MATIC delivers a driving experience characterized by smooth power delivery and effortless cruising. The abundant low-end torque from the diesel engine allows for brisk acceleration without the need for frequent downshifts. While not as overtly sporty as the gasoline-powered S 500, the S 320 CDI offers ample performance for most driving situations, achieving 0-60 mph in approximately 7.4 seconds and a governed top speed of 155 mph. The 7G-TRONIC transmission contributes to a refined driving experience, with seamless gear changes that are virtually imperceptible.
The 4MATIC all-wheel-drive system provides enhanced grip and stability, particularly on slippery surfaces. The suspension, typically utilizing Mercedes’ AIRMATIC air suspension system, offers a comfortable and controlled ride, absorbing bumps and imperfections in the road surface effectively. Compared to the S 350, the S 320 CDI offers superior fuel economy and a more relaxed driving experience due to the diesel engine’s torque characteristics. However, it lacks the outright acceleration and responsiveness of the higher-powered S 500.
Equipment & Trim Levels
The S 320 CDI 4MATIC came standard with a comprehensive array of luxury features, befitting its flagship status. Standard equipment typically included leather upholstery, power-adjustable front seats with memory function, dual-zone automatic climate control, a premium audio system, and a multi-function steering wheel. Safety features were also abundant, including anti-lock brakes (ABS), electronic stability control (ESP), and a suite of airbags.
Optional extras were plentiful, allowing buyers to customize their S-Class to their preferences. Popular options included a panoramic sunroof, rear seat entertainment system, massaging seats, a navigation system, and advanced parking assist features. Interior trim options included various wood veneers and aluminum accents. The S 320 CDI 4MATIC generally featured a more understated interior aesthetic compared to the more opulent S 500, focusing on refined elegance rather than overt luxury.
Chassis & Braking
The W221 S-Class chassis is a robust unit, designed to provide a comfortable and stable ride. The S 320 CDI 4MATIC typically featured AIRMATIC air suspension, which utilizes air springs and adaptive dampers to adjust the ride height and damping characteristics based on driving conditions. This system provides a smooth and controlled ride, while also allowing for adjustable ride height for improved ground clearance. The front suspension utilizes a multi-link design, while the rear suspension employs a multi-link independent suspension.
Braking duties are handled by ventilated disc brakes at all four corners. The braking system is augmented by ABS, ESP, and Brake Assist, providing excellent stopping power and stability. The S 320 CDI 4MATIC typically did not feature the larger brake rotors found on the higher-performance S 500 models, but the braking performance was still more than adequate for the vehicle’s weight and performance capabilities.
Market Reception & Comparison
The S 320 CDI 4MATIC was generally well-received by automotive critics, who praised its blend of luxury, performance, and fuel efficiency. The diesel engine was lauded for its smooth operation and abundant torque, while the 7G-TRONIC transmission was commended for its seamless gear changes. The 4MATIC all-wheel-drive system was also appreciated for its enhanced traction and stability.
Compared to its siblings, the S 320 CDI offered a compelling value proposition. It provided a similar level of luxury and refinement as the S 350, but with significantly better fuel economy. While it lacked the outright performance of the S 500, it offered a more relaxed and refined driving experience. In terms of reliability, the OM 642 diesel engine proved to be generally robust, although some owners have reported issues with the diesel particulate filter (DPF) and fuel injectors.
Technical Specifications
| Engine Model/Code | OM 642.930 |
| Engine Displacement | 2987 cm3 (182.28 cu. in.) |
| Number of Cylinders | 6 (V-engine) |
| Power | 235 Hp @ 3600 rpm |
| Torque | 540 Nm @ 1600 rpm (398.28 lb.-ft. @ 1600 rpm) |
| Fuel Type | Diesel |
| Fuel Consumption (Urban) | 12-12.2 l/100 km (19.6 – 19.3 US mpg) |
| Fuel Consumption (Extra Urban) | 7.1-7.3 l/100 km (33.1 – 32.2 US mpg) |
| Fuel Consumption (Combined) | 8.7-8.9 l/100 km (27 – 26.4 US mpg) |
| CO2 Emissions | 227-231 g/km |
| Acceleration 0-100 km/h | 7.8 sec |
| Acceleration 0-62 mph | 7.8 sec |
| Maximum Speed | 250 km/h (155.34 mph) |
| Kerb Weight | 1950 kg (4299.01 lbs.) |
| Fuel Tank Capacity | 90 l (23.78 US gal) |
| Transmission | 7-speed automatic (7G-TRONIC) |
| Drive Type | All-wheel drive (4MATIC) |
| Length | 5079 mm (199.96 in.) |
| Width | 1871 mm (73.66 in.) |
| Height | 1473 mm (57.99 in.) |
Legacy
The Mercedes-Benz S 320 CDI 4MATIC (W221) remains a desirable used car today, particularly for buyers seeking a luxurious and efficient grand tourer. The OM 642 diesel engine, while requiring regular maintenance, is generally considered to be reliable. Common issues, such as DPF clogging and fuel injector failures, can be addressed with proper maintenance and preventative measures. The 7G-TRONIC transmission is also generally reliable, although fluid changes are essential to maintain its smooth operation. The S 320 CDI 4MATIC represents a sweet spot in the W221 S-Class lineup, offering a compelling combination of luxury, performance, and fuel efficiency at a relatively affordable price point. Its enduring appeal is a testament to the quality of engineering and the timeless design of the Mercedes-Benz S-Class.
