The Mercedes-Benz S 350d 4MATIC, produced from May 2023 through 2026, represents a significant iteration within the W223 generation of the S-Class. This model, positioned as a mid-range offering in the lineup, combines a powerful diesel engine with mild-hybrid technology and all-wheel drive, delivering a blend of performance, efficiency, and luxury. It builds upon the foundation of the W223 platform (introduced in late 2020), which brought a substantial technological overhaul to the flagship sedan, focusing on advanced driver-assistance systems, a redesigned interior, and improved comfort. The S 350d EQ Boost 4MATIC specifically caters to buyers seeking a refined driving experience with reduced emissions compared to higher-powered gasoline variants.
Powertrain & Engine Architecture
At the heart of the S 350d lies the OM 656.830, a 3.0-liter inline-six cylinder diesel engine. This engine is a cornerstone of Mercedes-Benz’s modern diesel offerings, known for its robust construction and advanced technology. It features a sophisticated diesel commonrail fuel injection system, delivering precise fuel metering for optimal combustion. The engine utilizes a bi-turbocharger setup with an intercooler, maximizing power output and minimizing turbo lag. The valvetrain employs a Double Overhead Camshaft (DOHC) configuration with four valves per cylinder, contributing to efficient gas exchange and improved performance.
The “EQ Boost” designation indicates the integration of a 48-volt mild-hybrid system. This system incorporates a 23 horsepower electric motor integrated between the engine and the 9G-TRONIC automatic transmission. The electric motor doesn’t provide full electric drive capability but assists the engine during acceleration, smoothing out power delivery and reducing load on the internal combustion engine. It also enables features like extended coasting and regenerative braking, enhancing fuel efficiency. The system utilizes a 0.9 kWh lithium-ion battery for energy storage. The 9G-TRONIC automatic transmission, a nine-speed unit, is specifically tuned to complement the characteristics of the diesel engine and the EQ Boost system, offering smooth and efficient gear changes.
Engine Specifications
The OM 656.830 engine produces 313 horsepower at 3600-4800 rpm and a substantial 650 Nm (479.42 lb-ft) of torque between 1200-3200 rpm. This broad torque curve provides strong acceleration across a wide range of engine speeds. The engine boasts a high compression ratio of 15.5:1, contributing to its thermal efficiency. It also incorporates a particulate filter to minimize emissions, adhering to stringent Euro 6e emission standards.
Driving Characteristics
The S 350d 4MATIC delivers a refined and effortless driving experience. The combination of the powerful diesel engine, the EQ Boost system, and the 9G-TRONIC transmission results in smooth and responsive acceleration. The 0-100 km/h (0-62 mph) sprint is achieved in 5.5 seconds, and 0-60 mph in approximately 5.2 seconds, making it a surprisingly quick vehicle for its size and weight. The 9G-TRONIC transmission’s gear ratios are optimized for both fuel efficiency and performance, providing comfortable cruising at highway speeds while offering quick downshifts for overtaking maneuvers. Compared to the S 580 (gasoline V8) variant, the S 350d offers a more relaxed and fuel-efficient driving experience, albeit with slightly less outright acceleration. The lower weight over the front axle, due to the inline-six engine, contributes to balanced handling.
Equipment & Trim Levels
The S 350d 4MATIC comes standard with a comprehensive array of luxury features, befitting its flagship status. Standard interior appointments include high-quality leather upholstery, wood trim, and ambient lighting. The dashboard features the latest generation of Mercedes-Benz’s MBUX infotainment system, with a large touchscreen display and advanced voice control. Standard safety features include automatic emergency braking, lane-keeping assist, and adaptive cruise control. Optional extras available for the S 350d include premium sound systems, massaging seats, a head-up display, and a variety of interior customization options. Air suspension is standard, providing a supremely comfortable ride quality. The S 350d typically sits between the base S 450 and the higher-performance S 580 in terms of pricing and feature availability.
Chassis & Braking
The W223 S-Class utilizes an independent multi-link suspension system at both the front and rear axles. The S 350d is equipped with air suspension as standard, providing adjustable ride height and damping characteristics. This allows the driver to tailor the ride quality to their preferences, prioritizing comfort or sportiness. The braking system consists of ventilated discs on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) is standard, along with other electronic stability control systems. The S-Class also offers an optional 4-wheel steering system, enhancing maneuverability at low speeds and stability at high speeds.
Market Reception & Comparison
The S 350d 4MATIC has been generally well-received by automotive critics. It is praised for its refined driving experience, fuel efficiency, and luxurious interior. Compared to the gasoline-powered S-Class models, the S 350d offers significantly better fuel economy, achieving between 6.1 and 7.1 liters per 100 kilometers (38.6-33.1 US mpg). While the S 350d doesn’t offer the same level of outright performance as the S 580, it provides ample power for most driving situations. Reliability has been generally good, although, as with any complex vehicle, potential issues can arise with the advanced electronic systems. The diesel engine itself is known for its durability, but regular maintenance is crucial.
Technical Specifications
| Body type | Sedan, 4 Doors, 5 Seats |
| Fuel economy | 6.1-7.1 l/100 km (38.6 – 33.1 US mpg, 46.3 – 39.8 UK mpg, 16.4 – 14.1 km/l) |
| CO2 emissions | 160-186 g/km |
| Fuel Type | Diesel |
| Acceleration 0-100 km/h | 5.5 sec |
| Acceleration 0-62 mph | 5.5 sec |
| Acceleration 0-60 mph | 5.2 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 6e |
| Weight-to-power ratio | 6.5 kg/Hp, 152.7 Hp/tonne |
| Weight-to-torque ratio | 3.2 kg/Nm, 317.1 Nm/tonne |
| Gross battery capacity | 0.9 kWh |
| Battery voltage | 48 V |
| Battery technology | Lithium-ion (Li-Ion) |
| Electric motor power | 23 Hp |
| Electric motor Torque | 250 Nm (184.39 lb.-ft.) |
| Power | 313 Hp @ 3600-4800 rpm |
| Torque | 650 Nm @ 1200-3200 rpm (479.42 lb.-ft. @ 1200-3200 rpm) |
| Engine displacement | 2989 cm3 (182.4 cu. in.) |
| Number of cylinders | 6 |
| Compression ratio | 15.5:1 |
| Fuel injection system | Diesel Commonrail |
| Engine oil capacity | 9 l (9.51 US qt | 7.92 UK qt) |
| Kerb Weight | 2050 kg (4519.48 lbs.) |
| Max. weight | 2820 kg (6217.04 lbs.) |
| Trunk (boot) space | 540 l (19.07 cu. ft.) |
| Fuel tank capacity | 65 l (17.17 US gal | 14.3 UK gal) |
| Number of gears | 9 |
| Gearbox type | automatic transmission G-TRONIC |
| Length | 5179 mm (203.9 in.) |
| Width | 1954 mm (76.93 in.) |
| Height | 1503 mm (59.17 in.) |
Legacy
The OM 656 engine family, including the version found in the S 350d, has proven to be a reliable and durable powertrain. While modern diesel engines are complex and require diligent maintenance, the OM 656 has generally demonstrated good longevity. On the used car market, the W223 S 350d 4MATIC is becoming increasingly desirable due to its blend of luxury, performance, and fuel efficiency. Its relatively lower running costs compared to the gasoline variants make it an attractive option for buyers seeking a high-end sedan. As with any used vehicle, a thorough inspection and maintenance history review are essential before purchase.
