The Mercedes-Benz C 300d EQ Boost, introduced in 2021 as part of the W206 C-Class generation, represents a significant step in the brand’s commitment to efficient performance and mild hybridization. Positioned as a mid-range offering within the C-Class lineup, it bridges the gap between the entry-level C 200 and the more performance-oriented AMG variants. This model combines a 2.0-liter turbocharged diesel engine with a 48-volt mild hybrid system, paired exclusively with the 9G-TRONIC nine-speed automatic transmission. The W206 C-Class, built on an updated version of the MRA2 platform, aimed to deliver enhanced refinement, technology, and driving dynamics compared to its predecessor.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | C-class |
| Generation | C-class (W206) |
| Type (Engine) | C 300d (265 Hp) EQ Boost 9G-TRONIC |
| Start of production | 2021 year |
| Powertrain Architecture | MHEV (Mild Hybrid Electric Vehicle) |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Combined fuel consumption (WLTP) | 5-5.6 l/100 km (47 – 42 US mpg) |
| CO2 emissions (WLTP) | 131-148 g/km |
| Fuel consumption (economy) – urban (NEDC) | 6.8-7.1 l/100 km (34.6 – 33.1 US mpg) |
| Fuel consumption (economy) – extra urban (NEDC) | 3.9-4.2 l/100 km (60.3 – 56 US mpg) |
| Fuel consumption (economy) – combined (NEDC) | 5-5.3 l/100 km (47 – 44.4 US mpg) |
| CO2 emissions (NEDC) | 132-139 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 5.7 sec |
| Acceleration 0 – 62 mph | 5.7 sec |
| Acceleration 0 – 60 mph | 5.4 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 6d-ISC-FCM |
| Weight-to-power ratio | 6.4 kg/Hp |
| Weight-to-torque ratio | 3.1 kg/Nm |
| Gross battery capacity | 0.9 kWh |
| Battery voltage | 48 V |
| Battery technology | Lithium-ion (Li-Ion) |
| Electric motor power | 20 Hp |
| Electric motor Torque | 200 Nm (147.51 lb.-ft.) |
| Power | 265 Hp @ 4200 rpm |
| Torque | 550 Nm @ 1800-2200 rpm (405.66 lb.-ft. @ 1800-2200 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | OM 654.820 |
| Engine displacement | 1992 cm3 (121.56 cu. in.) |
| Number of cylinders | 4 |
| Engine configuration | Inline |
| Cylinder Bore | 82 mm (3.23 in.) |
| Piston Stroke | 94.3 mm (3.71 in.) |
| 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 | 6 l (6.34 US qt | 5.28 UK qt) |
| Kerb Weight | 1700 kg (3747.86 lbs.) |
| Max. weight | 2380 kg (5247 lbs.) |
| Max load | 680 kg (1499.14 lbs.) |
| Trunk (boot) space – minimum | 455 l (16.07 cu. ft.) |
| Fuel tank capacity | 50 l (13.21 US gal | 11 UK gal) |
| Length | 4751 mm (187.05 in.) |
| Width | 1820 mm (71.65 in.) |
| Height | 1437 mm (56.57 in.) |
| Wheelbase | 2865 mm (112.8 in.) |
| Front track | 1582-1601 mm (62.28 – 63.03 in.) |
| Rear track | 1594-1613 mm (62.76 – 63.5 in.) |
| Drag coefficient (Cd) | 0.24 |
| Minimum turning circle | 10.64 m (34.91 ft.) |
| Gearbox | 9 gears, automatic transmission G-TRONIC |
Powertrain & Engine Architecture
The heart of the C 300d EQ Boost is the OM 654.820, a 2.0-liter inline-four cylinder diesel engine. This engine utilizes a twin-turbocharger setup, incorporating a variable geometry turbocharger (VGT) and a smaller turbocharger, to deliver both strong low-end torque and high-end power. The engine employs a common-rail direct fuel injection system operating at extremely high pressures (2700 bar) for optimized combustion. The DOHC valvetrain with four valves per cylinder further enhances breathing and efficiency. The “EQ Boost” component refers to a 48-volt mild hybrid system. This system incorporates a belt-driven integrated starter-generator (ISG) that adds up to 20 horsepower and 200 Nm (147.51 lb-ft) of torque, assisting the engine during acceleration and allowing for smoother start/stop operation. The 9G-TRONIC nine-speed automatic transmission is standard, offering quick and seamless gear changes. It’s designed to work in conjunction with the mild hybrid system, optimizing efficiency and responsiveness.
Driving Characteristics
The C 300d EQ Boost delivers a refined and responsive driving experience. The combination of the turbocharged diesel engine and the electric boost provides ample torque from low engine speeds, resulting in strong acceleration. The 0-60 mph sprint takes approximately 5.4 seconds. The 9G-TRONIC transmission contributes to smooth gear changes, and the mild hybrid system helps to fill in any gaps in torque delivery. Compared to the C 200, the C 300d offers significantly more power and torque, resulting in a more effortless driving experience, particularly when fully loaded or tackling inclines. While not as overtly sporty as the AMG-tuned models, the C 300d provides a good balance of performance and efficiency. The steering is precise and well-weighted, and the suspension offers a comfortable ride without sacrificing handling.
Equipment & Trim Levels
The C 300d EQ Boost typically came well-equipped as a mid-range trim. Standard features generally included Mercedes-Benz User Experience (MBUX) infotainment system with a large touchscreen display, digital instrument cluster, leather upholstery, heated front seats, automatic climate control, and a suite of advanced driver-assistance systems (ADAS) such as adaptive cruise control, lane-keeping assist, and automatic emergency braking. Optional extras included a panoramic sunroof, premium sound system, head-up display, and various interior trim options. The interior design emphasized luxury and modernity, with high-quality materials and a minimalist aesthetic.
Chassis & Braking
The W206 C-Class utilizes a sophisticated chassis design featuring a four-link front suspension and a multi-link rear suspension. The suspension is tuned to provide a comfortable ride while maintaining good handling characteristics. The C 300d typically came equipped with ventilated disc brakes on all four wheels, providing ample stopping power. ABS (Anti-lock Braking System) is standard, along with electronic stability control. Some models were available with optional 4-wheel steering, which enhances agility at low speeds and stability at high speeds.
Market Reception & Comparison
The C 300d EQ Boost was generally well-received by automotive critics. It was praised for its refined engine, smooth transmission, comfortable ride, and advanced technology. Fuel economy was also a strong point, with the mild hybrid system contributing to improved efficiency. Compared to the C 200, the C 300d offered a noticeable performance upgrade, making it a more appealing option for drivers who prioritize power and responsiveness. Compared to gasoline-powered C-Class models, the C 300d offered superior fuel economy and torque. However, some critics noted that the diesel engine could be slightly noisier than its gasoline counterparts.
Legacy
The OM 654 engine family, including the version used in the C 300d, has proven to be a reliable and durable powertrain. The mild hybrid system adds a layer of complexity, but early reports suggest that it has also been relatively trouble-free. On the used car market, the W206 C 300d EQ Boost holds its value well, thanks to its combination of performance, efficiency, and luxury. It remains a popular choice for buyers seeking a refined and capable mid-size sedan. The integration of mild hybrid technology in this model paved the way for Mercedes-Benz’s broader electrification strategy.
