2023-2026 Mercedes-Benz S-class (W223) S 450d (367 Hp) EQ Boost 4MATIC 9G-TRONIC

The Mercedes-Benz S 450d 4MATIC, introduced in May 2023 as part of the W223 generation of the S-Class, represents a diesel-powered variant positioned within the luxury sedan’s lineup. Utilizing a mild hybrid system (EQ Boost), this model aimed to balance performance with improved fuel efficiency. Production is anticipated to continue through 2026. The W223 S-Class, overall, represents the sixth generation of the flagship Mercedes-Benz sedan, building upon a legacy of innovation and luxury. The S 450d specifically caters to buyers seeking a refined driving experience with the torque characteristics of a diesel engine, coupled with advanced technology and the prestige associated with the S-Class nameplate.

S 450d: Positioning and Overview

The S 450d 4MATIC occupies a middle ground within the W223 S-Class range. Above it sit the more powerful S 580 and AMG-tuned models, while below it are typically base-level S 350 or S 400d variants (depending on regional availability). The S 450d was designed to appeal to customers who prioritize fuel economy and strong low-end torque for comfortable long-distance cruising, without sacrificing the luxury and technological features expected of an S-Class. It offered a compelling alternative to the gasoline-powered options, particularly in European markets where diesel fuel remains popular. The inclusion of the EQ Boost system further enhances efficiency and provides a subtle performance boost.

Powertrain & Engine Architecture

At the heart of the S 450d 4MATIC lies the OM 656.830, a 3.0-liter inline-six cylinder diesel engine. This engine is a highly advanced design, featuring a sophisticated commonrail direct fuel injection system operating at pressures up to 2,700 bar. This high-pressure injection ensures efficient combustion and minimizes particulate emissions. The engine utilizes a bi-turbocharger setup with a variable geometry turbine (VGT) and a conventional turbocharger, working in tandem to deliver both strong low-end torque and high-end power. The engine also incorporates an intercooler to further enhance performance. The valvetrain employs a double overhead camshaft (DOHC) configuration with four valves per cylinder, optimizing gas flow for improved efficiency and power output.

The “EQ Boost” component of the powertrain consists of a 48-volt integrated starter-generator (ISG). This ISG provides several functions: it enables a near-instantaneous and silent engine start/stop system, it allows for regenerative braking to recapture energy, and it can deliver a temporary power boost of 23 hp and 250 Nm (184.39 lb.-ft.) to assist the engine during acceleration. The ISG is connected to a 0.9 kWh lithium-ion battery. The engine is mated to Mercedes-Benz’s 9G-TRONIC nine-speed automatic transmission. This transmission is known for its smooth shifting and wide gear ratio spread, contributing to both fuel efficiency and refined driving dynamics. The transmission is electronically controlled and adapts its shift points based on driving conditions and driver input.

Driving Characteristics

The S 450d 4MATIC delivers a characteristically smooth and refined driving experience. The inline-six diesel engine provides a substantial 750 Nm (553.17 lb.-ft.) of torque available from as low as 1350 rpm, resulting in effortless acceleration and strong passing power. While not as overtly sporty as the higher-output gasoline variants, the S 450d offers a 0-60 mph acceleration time of approximately 4.8 seconds, and a 0-100 km/h time of 5 seconds. The 9G-TRONIC transmission contributes to this performance with its quick and seamless gear changes. The EQ Boost system provides a noticeable, though subtle, boost during acceleration, enhancing responsiveness. The air suspension, standard on the S-Class, further contributes to ride comfort, absorbing bumps and imperfections in the road surface effectively. The 4MATIC all-wheel-drive system provides excellent traction in all weather conditions, enhancing stability and control.

Equipment & Trim Levels

The S 450d 4MATIC typically comes standard with a comprehensive array of luxury features. Interior upholstery is generally leather, with a wide range of color options available. The dashboard features Mercedes-Benz’s MBUX infotainment system, with a large touchscreen display and advanced voice control. Standard equipment includes features such as heated and ventilated front seats, a panoramic sunroof, ambient lighting, and a premium sound system. Optional extras include features such as rear-seat entertainment, massaging seats, a head-up display, and advanced driver-assistance systems like adaptive cruise control and lane-keeping assist. Trim levels beyond the base model often included different wood or metal trim options, upgraded leather upholstery, and exclusive exterior styling elements.

Chassis & Braking

The W223 S-Class utilizes an independent multi-link suspension system at both the front and rear axles. The air suspension, standard on the S 450d, provides adjustable ride height and damping, allowing drivers to tailor the suspension to their preferences. The S 450d is equipped with ventilated disc brakes on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) is standard, along with electronic brake-force distribution and brake assist. The S-Class also offers an optional 4-wheel steering system, which enhances maneuverability at low speeds and improves stability at high speeds. Stabilizer bars are fitted to both the front and rear axles to reduce body roll during cornering.

Market Reception & Comparison

The S 450d 4MATIC was generally well-received by automotive critics. It was praised for its refined driving experience, strong fuel economy, and luxurious interior. Compared to the gasoline-powered S 450 or S 500 models, the S 450d offered comparable performance with significantly better fuel efficiency. However, some critics noted that the diesel engine lacked the smoothness and responsiveness of the gasoline engines. In terms of reliability, the OM 656 engine family has proven to be robust and durable, although diesel engines generally require more frequent maintenance than gasoline engines, particularly regarding the diesel particulate filter (DPF). Compared to other luxury sedans in its class, such as the BMW 7 Series and Audi A8, the S 450d 4MATIC offered a compelling combination of performance, luxury, and efficiency.

Technical Specifications

Legacy

The OM 656 engine family, including the version used in the S 450d 4MATIC, has established a reputation for reliability and longevity. While diesel engines require diligent maintenance, particularly concerning the DPF system, these engines are generally capable of high mileage with proper care. On the used car market, the S 450d 4MATIC represents a compelling value proposition, offering a significant amount of luxury and technology for its price. However, potential buyers should be aware of the potential maintenance costs associated with a diesel engine and ensure that the vehicle has been properly maintained. The S 450d’s blend of performance, efficiency, and luxury ensures its continued appeal in the used car market for years to come.