2009-2010 Mercedes-Benz S-class (W221 facelift ) S 350 CDI BlueEFFICIENCY (235 Hp) G-TRONIC

The Mercedes-Benz S 350 CDI BlueEFFICIENCY, produced from 2009 to 2010, was a diesel-powered variant of the W221 S-Class, representing the facelifted third generation of the flagship sedan. Positioned as a mid-range offering within the W221 lineup, it bridged the gap between the entry-level S 300 CDI and the more powerful S 500 models. This variant aimed to provide a balance of luxury, performance, and fuel efficiency, appealing to buyers seeking a sophisticated grand tourer with lower running costs than its gasoline counterparts. The S 350 CDI BlueEFFICIENCY was built on the 1HX0 platform, shared with other high-end Mercedes-Benz vehicles of the era.

Powertrain & Engine Architecture

The heart of the S 350 CDI BlueEFFICIENCY is the OM642.930 3.0-liter V6 diesel engine. This engine is a longitudinally mounted, turbocharged and intercooled common rail direct injection diesel. It produces 235 horsepower at 3600 rpm and a substantial 398.28 lb-ft of torque between 1600 and 2400 rpm. The engine features a compression ratio of 17.7:1 and 4 valves per cylinder. The common rail direct injection system, operating at extremely high pressures, optimizes fuel atomization for improved combustion efficiency and reduced emissions. The turbocharger, coupled with an intercooler, enhances power output by forcing more air into the cylinders.

Paired with the engine is the 7G-TRONIC seven-speed automatic transmission. This transmission, a staple in Mercedes-Benz vehicles, is known for its smooth shifting and efficiency. It features a torque converter and electronically controlled gear changes. The 7G-TRONIC allows for both fully automatic operation and manual gear selection via steering wheel-mounted paddles or the gear selector. The transmission’s gear ratios are optimized to deliver strong acceleration while maintaining low engine speeds for improved fuel economy.

BlueEFFICIENCY Technology

The “BlueEFFICIENCY” designation signifies a suite of technologies aimed at reducing fuel consumption and emissions. These included optimized aerodynamics, reduced rolling resistance tires, and an improved engine management system. The engine also incorporated a particulate filter to minimize soot emissions, and a closed-loop exhaust gas recirculation (EGR) system to reduce nitrogen oxide (NOx) emissions.

Driving Characteristics

The S 350 CDI BlueEFFICIENCY offered a distinctly different driving experience compared to the gasoline-powered S-Class models. While lacking the outright acceleration of the V8 or V12 variants, the diesel engine’s abundant torque provided strong and readily available power throughout the rev range. Acceleration from 0 to 60 mph was achieved in approximately 7.4 seconds, and 0-100 km/h in 7.8 seconds. The 7G-TRONIC transmission contributed to smooth and seamless gear changes, enhancing the overall driving comfort.

Compared to the S 300 CDI, the S 350 CDI offered a noticeable performance increase due to its larger displacement and higher power output. However, it didn’t possess the same level of responsiveness as the higher-output gasoline engines. The S 350 CDI was primarily geared towards relaxed, long-distance cruising, where its torque and fuel efficiency were most appreciated. The rear-wheel drive configuration provided a balanced handling characteristic, typical of large luxury sedans.

Equipment & Trim Levels

The S 350 CDI BlueEFFICIENCY came standard with a comprehensive array of luxury features. Interior appointments typically included leather upholstery, wood trim, and a multi-function steering wheel. Standard equipment also included automatic climate control, a premium audio system, power-adjustable seats with memory function, and a sunroof. Safety features were abundant, including ABS, electronic stability control, multiple airbags, and a tire pressure monitoring system.

Optional extras were plentiful, allowing buyers to customize their S-Class to their preferences. These included features such as a rear seat entertainment system, massaging seats, a panoramic sunroof, advanced parking assist systems, and upgraded leather options. The S 350 CDI BlueEFFICIENCY could be equipped with Mercedes-Benz’s AIRMATIC suspension system, which provided adjustable ride height and damping for enhanced comfort and handling.

Chassis & Braking

The W221 S-Class chassis featured a sophisticated suspension system designed to provide a smooth and comfortable ride. The S 350 CDI BlueEFFICIENCY utilized a four-wheel independent suspension with coil springs and shock absorbers. The front suspension employed a multi-link design, while the rear suspension featured a modified multi-link setup. Stabilizer bars were fitted to both the front and rear axles to reduce body roll during cornering.

Braking duties were handled by disc brakes on all four wheels, equipped with ABS (Anti-lock Braking System) and electronic brake-force distribution. The braking system provided ample stopping power and control. The S 350 CDI BlueEFFICIENCY typically rode on 17-inch alloy wheels with 235/55 R17 tires.

Market Reception & Comparison

The S 350 CDI BlueEFFICIENCY was generally well-received by automotive critics. It was praised for its refined ride, luxurious interior, and impressive fuel economy for a vehicle of its size and class. The diesel engine’s torque was also a highlight, providing effortless acceleration and strong passing power. However, some critics noted that the engine lacked the refinement and responsiveness of the gasoline-powered S-Class models.

Compared to the S 300 CDI, the S 350 CDI offered a noticeable performance upgrade, making it a more appealing option for drivers who desired a bit more power. In terms of fuel economy, the S 350 CDI achieved a combined fuel consumption of 7.6 l/100 km (30.9 US mpg), making it a relatively efficient luxury sedan. Its CO2 emissions ranged from 199-201 g/km. Reliability was generally good, although diesel engines can be more susceptible to issues with the fuel injection system and particulate filter over time.

Technical Specifications

Legacy

The OM642 engine family, including the OM642.930 found in the S 350 CDI BlueEFFICIENCY, has proven to be relatively durable and reliable when properly maintained. However, like all diesel engines, it is susceptible to issues with the fuel injection system, turbocharger, and particulate filter, particularly as mileage increases. In the used car market, the S 350 CDI BlueEFFICIENCY represents a compelling value proposition for buyers seeking a luxurious and fuel-efficient grand tourer. Its lower purchase price compared to gasoline-powered S-Class models, combined with its strong torque and comfortable ride, make it an attractive option for those willing to accept the potential maintenance costs associated with a diesel engine.

Today, these vehicles are increasingly sought after by enthusiasts who appreciate the unique blend of luxury, performance, and efficiency that the S 350 CDI BlueEFFICIENCY offers. While newer S-Class models have moved towards more advanced engine technologies, the W221 S 350 CDI BlueEFFICIENCY remains a testament to Mercedes-Benz’s engineering prowess and its commitment to providing a refined and enjoyable driving experience.