The Mercedes-Benz S-Class Long (V223) S 350d EQ Boost 4MATIC 9G-TRONIC, launched in May 2023, represents a significant iteration of the flagship S-Class sedan. Positioned as a mid-range offering within the V223 generation, which debuted in late 2020, the S 350d balances luxury, performance, and efficiency through the integration of mild hybrid technology. The “Long” designation indicates an extended wheelbase, primarily aimed at markets where rear passenger space is highly valued, such as China. This variant is designed to appeal to buyers seeking a sophisticated and technologically advanced luxury vehicle with a diesel powertrain, offering a compelling alternative to petrol-powered S-Class models. Production is expected to continue through 2026.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | S-class |
| Generation | S-class Long (V223) |
| Type | S 350d (313 Hp) EQ Boost 4MATIC 9G-TRONIC |
| Start of production | May, 2023 |
| End of production | 2026 |
| Powertrain Architecture | MHEV (Mild Hybrid Electric Vehicle) |
| Body type | Sedan |
| Seats | 4-5 |
| Doors | 4 |
| Combined fuel consumption (WLTP) | 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 (WLTP) | 161-186 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 | 6.6 kg/Hp, 151.2 Hp/tonne |
| Weight-to-torque ratio | 3.2 kg/Nm, 314 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.) |
| Electric motor location | Between the combustion engine and the transmission |
| Power | 313 Hp @ 3600-4800 rpm |
| Power per litre | 104.7 Hp/l |
| Torque | 650 Nm @ 1200-3200 rpm (479.42 lb.-ft. @ 1200-3200 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | OM 656.830 |
| Engine displacement | 2989 cm3 (182.4 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Compression ratio | 15.5:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | BiTurbo, Intercooler |
| Valvetrain | DOHC |
| Engine oil capacity | 9 l (9.51 US qt | 7.92 UK qt) |
| Coolant | 12 l (12.68 US qt | 10.56 UK qt) |
| Kerb Weight | 2070 kg (4563.57 lbs.) |
| Max. weight | 2820 kg (6217.04 lbs.) |
| Max load | 750 kg (1653.47 lbs.) |
| Trunk (boot) space – minimum | 540 l (19.07 cu. ft.) |
| Fuel tank capacity | 65 l (17.17 US gal | 14.3 UK gal) |
| AdBlue tank | 25 l (6.6 US gal | 5.5 UK gal) |
| Max. roof load | 100 kg (220.46 lbs.) |
| Permitted trailer load with brakes (12%) | 2100 kg (4629.71 lbs.) |
| Permitted trailer load without brakes | 750 kg (1653.47 lbs.) |
| Permitted towbar download | 85 kg (187.39 lbs.) |
| Length | 5289 mm (208.23 in.) |
| Width | 1954 mm (76.93 in.) |
| Width including mirrors | 2109 mm (83.03 in.) |
| Height | 1503 mm (59.17 in.) |
| Wheelbase | 3216 mm (126.61 in.) |
| Front track | 1655 mm (65.16 in.) |
| Rear (Back) track | 1651 mm (65 in.) |
| Front overhang | 877 mm (34.53 in.) |
| Rear overhang | 1196 mm (47.09 in.) |
| Ride height (ground clearance) | 130 mm (5.12 in.) |
| Minimum turning circle (turning diameter) | 10.9 m (35.76 ft.) |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Front suspension | Independent multi-link suspension, Air suspension |
| Rear suspension | Independent multi-link suspension, Air suspension |
| Gearbox | 9 gears, automatic transmission G-TRONIC |
Powertrain & Engine Architecture
The S 350d is powered by 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 refinement and efficiency. It utilizes a sophisticated diesel commonrail fuel injection system, delivering fuel at extremely high pressures for optimized combustion. The engine features a bi-turbocharger setup with an intercooler, enhancing both power and torque across a broad RPM range. The valvetrain employs a Double Overhead Camshaft (DOHC) design with four valves per cylinder, contributing to efficient gas exchange. Crucially, this engine is paired with a 48-volt mild hybrid system (EQ Boost). This system incorporates a 23 horsepower electric motor integrated between the engine and the 9G-TRONIC automatic transmission. The electric motor provides assistance during acceleration, allowing for smoother starts and improved fuel economy. The 9G-TRONIC transmission itself is a nine-speed automatic, known for its smooth shifts and wide gear ratio spread, optimizing both performance and fuel efficiency.
Driving Characteristics
The S 350d delivers a refined and effortless driving experience. The combination of the 313 hp diesel engine and the EQ Boost system provides ample torque (650 Nm / 479.42 lb-ft) from low engine speeds, resulting in strong acceleration. The 0-60 mph sprint takes approximately 5.2 seconds. While not as overtly sporty as some of the petrol-powered S-Class variants, the S 350d offers more than sufficient performance for comfortable and confident highway cruising. The 9G-TRONIC transmission contributes to smooth gear changes, and the mild hybrid system helps to mask any turbo lag. Compared to higher-output S-Class models, the S 350d prioritizes fuel efficiency and relaxed cruising over outright performance. The gear ratios are tuned for optimal fuel economy at highway speeds, while still providing responsive acceleration when needed.
Equipment & Trim Levels
The S 350d Long typically comes standard with a comprehensive suite of luxury features. These include premium leather upholstery, heated and ventilated front and rear seats, a Burmester surround sound system, and a large touchscreen infotainment system with Mercedes-Benz’s MBUX interface. Standard safety features include adaptive cruise control, lane keeping assist, automatic emergency braking, and a 360-degree camera system. Optional extras often include a rear-seat entertainment system, massaging seats, and various interior trim upgrades. The long wheelbase provides significantly increased rear legroom, enhancing the comfort of rear passengers. The interior design emphasizes a minimalist aesthetic with high-quality materials and meticulous attention to detail.
Chassis & Braking
The S 350d Long utilizes an independent multi-link suspension system at both the front and rear, coupled with Mercedes-Benz’s AIRMATIC air suspension. This combination provides a remarkably comfortable ride, effectively absorbing bumps and imperfections in the road surface. The air suspension also allows for adjustable ride height, enhancing both comfort and off-road capability (though the S-Class is rarely taken off-road). Braking duties are handled by ventilated discs at all four corners, providing ample stopping power. The vehicle is equipped with ABS (Anti-lock Braking System) and other advanced braking assistance systems. The 4MATIC all-wheel-drive system ensures optimal traction in all weather conditions.
Market Reception & Comparison
The S 350d EQ Boost 4MATIC 9G-TRONIC has been generally well-received by automotive critics. It is praised for its refined driving experience, luxurious interior, and impressive fuel economy. Compared to the S 450 or S 580 models, the S 350d offers a more economical option without sacrificing a significant amount of performance. The diesel engine provides excellent torque, making it well-suited for long-distance driving. However, some critics note that the diesel engine is not as smooth or refined as the petrol engines offered in the S-Class lineup. Fuel economy figures of 6.1-7.1 l/100 km (38.6 – 33.1 US mpg) are competitive within the luxury sedan segment.
Legacy
The OM 656 engine family, including the OM 656.830 found in the S 350d, has proven to be a reliable and durable powertrain. Mercedes-Benz has a long history of producing high-quality diesel engines, and the OM 656 continues that tradition. The integration of mild hybrid technology further enhances the engine’s efficiency and reduces emissions. In the used car market, the S 350d is expected to hold its value well due to its combination of luxury, performance, and fuel economy. The long wheelbase version will likely be particularly desirable in markets where rear passenger space is a priority. Proper maintenance, including regular servicing and AdBlue refills, will be crucial to ensuring the long-term reliability of this powertrain.
