The Mercedes-Benz S 320 CDI, produced between 1999 and 2002, was a diesel-powered variant of the W220 S-Class, representing a significant offering in the luxury sedan segment. Utilizing a 3.2-liter inline-six cylinder engine paired with a 5G-TRONIC automatic transmission, the S 320 CDI aimed to provide a blend of performance, efficiency, and the renowned comfort associated with the S-Class nameplate. It occupied a middle ground within the W220 lineup, positioned between the entry-level S 280/320 gasoline models and the higher-performance S 430/500 and S 55 AMG variants.
The W220 S-Class and the S 320 CDI’s Role
The W220 S-Class, launched in 1998, was a technologically advanced vehicle for its time, introducing innovations like DISTRONIC adaptive cruise control, BAS brake assist, and an active body control suspension. The S 320 CDI was introduced as a diesel option to cater to European markets where diesel engines were – and continue to be – highly popular due to their fuel efficiency and torque characteristics. In the US market, diesel passenger cars were less common, and the S 320 CDI was not officially offered. The CDI designation signified “Common Rail Direct Injection,” highlighting the advanced fuel delivery system employed by the engine.
Powertrain & Engine Architecture
The heart of the S 320 CDI is the OM 613.960 3.2-liter inline-six cylinder diesel engine. This engine is characterized by its robust construction and advanced technology for the period. It features a cast iron block and aluminum cylinder head, contributing to its durability. The engine utilizes a second-generation common rail direct injection system, delivering fuel at extremely high pressures (1,350 bar) for optimized combustion. This system, developed by Bosch, allowed for precise fuel metering and improved efficiency. The engine also incorporates a variable geometry turbocharger (VGT) and an intercooler to enhance power output and reduce turbo lag. The VGT adjusts the turbine vanes to optimize airflow for different engine speeds, improving both low-end torque and high-end power.
The 5G-TRONIC automatic transmission, a five-speed unit developed by Mercedes-Benz, was specifically calibrated to work with the characteristics of the diesel engine. It features a torque converter and electronically controlled gear changes, providing smooth and responsive shifting. The transmission’s gear ratios were optimized to maximize fuel efficiency and provide adequate acceleration. The 5G-TRONIC also included a manual shift mode, allowing drivers to exert more control over gear selection.
Engine Specifications (OM 613.960)
- Displacement: 3,227 cc (196.92 cu in)
- Bore x Stroke: 88 mm x 88.4 mm (3.46 in x 3.48 in)
- Compression Ratio: 18:1
- Valvetrain: 4 valves per cylinder
- Fuel Injection: Diesel Common Rail
- Turbocharging: Variable Geometry Turbocharger (VGT) with Intercooler
Driving Characteristics
The S 320 CDI offered a distinctly different driving experience compared to its gasoline-powered siblings. While lacking the outright acceleration of the S 430 or S 500, the S 320 CDI delivered substantial torque – 470 Nm (346.65 lb-ft) – from low engine speeds. This made it particularly well-suited for effortless cruising and overtaking maneuvers. The 5G-TRONIC transmission contributed to a smooth and refined driving experience, although it could sometimes feel slightly hesitant during quick downshifts. Acceleration from 0 to 100 km/h (0-62 mph) took approximately 8.8 seconds, and top speed was electronically limited to 230 km/h (142.92 mph). The engine’s torque curve provided strong pull throughout the rev range, making it a comfortable and capable grand tourer.
Equipment & Trim Levels
As a flagship sedan, the W220 S-Class, including the S 320 CDI, came standard with a comprehensive array of luxury features. Standard equipment typically included leather upholstery, automatic climate control, power-adjustable seats with memory function, a premium sound system, and wood trim. The S 320 CDI also benefited from the advanced safety features of the W220 platform, such as ABS, traction control, and multiple airbags. Optional extras included a sunroof, navigation system, upgraded sound systems (often Bose or Harman Kardon), rear seat entertainment, and various interior trim options. The level of standard equipment was generally high, reflecting the S-Class’s position as a luxury vehicle.
Chassis & Braking
The W220 S-Class featured a fully independent suspension system, utilizing double wishbones at the front and a multi-link setup at the rear. This suspension design provided a comfortable ride and excellent handling characteristics. The S 320 CDI, being a heavier vehicle due to the diesel engine, often featured slightly stiffer spring rates and dampers compared to the lighter gasoline models. Braking duties were handled by ventilated disc brakes at the front and solid disc brakes at the rear. ABS (Anti-lock Braking System) was standard, providing enhanced braking performance and stability. The steering system was a hydraulic power-assisted rack and pinion setup, offering precise and responsive steering feel.
Market Reception & Comparison
The S 320 CDI was well-received in European markets, where diesel engines were favored for their fuel efficiency and torque. Critics praised the car’s comfortable ride, refined interior, and strong performance. However, some reviewers noted that the diesel engine was slightly noisier than the gasoline alternatives. Compared to the S 430, the S 320 CDI offered comparable levels of luxury and comfort but with lower running costs. Compared to the S 280/320 gasoline models, the S 320 CDI provided significantly more torque and better fuel economy, albeit with a slightly higher purchase price. Fuel economy figures were around 8 l/100 km (29.4 US mpg) combined, and CO2 emissions were rated at 212 g/km.
Technical Specifications
| Body Type | Sedan, 4 Doors, 5 Seats |
| Engine Type | Diesel, Inline-6 |
| Engine Displacement | 3,227 cm3 (196.92 cu in) |
| Power Output | 197 Hp @ 4200 rpm |
| Torque | 470 Nm @ 1800-2600 rpm (346.65 lb-ft) |
| Transmission | 5-speed Automatic (5G-TRONIC) |
| Drive Type | Rear Wheel Drive |
| Acceleration 0-100 km/h | 8.8 sec |
| Top Speed | 230 km/h (142.92 mph) |
| Fuel Consumption (Combined) | 8 l/100 km (29.4 US mpg) |
| CO2 Emissions | 212 g/km |
| Kerb Weight | 1830 kg (4034.46 lbs) |
| Fuel Tank Capacity | 88 l (23.25 US gal) |
| Length | 5038 mm (198.35 in) |
| Width | 1855 mm (73.03 in) |
Legacy
The OM 613 engine family, including the OM 613.960 found in the S 320 CDI, is known for its durability and reliability. With proper maintenance, these engines can accumulate high mileage. However, like all diesel engines, they are susceptible to issues with the fuel injection system and turbocharger over time. In the used car market, the W220 S 320 CDI is often sought after by those looking for a comfortable and fuel-efficient luxury sedan. Its relative rarity (due to not being officially sold in the US) and the robust nature of the engine contribute to its continued appeal. While maintenance costs can be higher than for gasoline-powered vehicles, the S 320 CDI remains a compelling option for discerning buyers seeking a classic Mercedes-Benz experience.
