The Mercedes — Benz M 257.920 is a 2,999 cc, inline — six, turbocharged petrol engine produced between 2017 and present. It features a 30° canted inline — six configuration with twin — scroll turbocharging, 48 — volt EQ Boost mild hybrid system, and direct fuel injection at up to 350 bar, delivering 270 kW (367 PS) in standard tuning, with peak torque of 500 Nm available from 1,800 to 5,800 rpm.
Fitted to mid — size and full — size luxury sedans and SUVs such as the W222 S — Class, W213 E…
All production units (2017–present) meet Euro 6d-TEMP emissions standards . No non-compliant variant was produced.
The Mercedes-Benz M 257.920 is a 2,999 cc inline-six engineered for premium sedans and SUVs (2017–present). It combines a DOHC 24-valve layout with twin-scroll turbocharging and 48-volt EQ Boost system to deliver refined, responsive performance. Designed to meet Euro 6d-TEMP standards, it balances electrified efficiency with strong torque delivery.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,999 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Turbocharged | |
Bore × stroke | 83.0 mm × 92.0 mm | |
Power output | 270 kW (367 PS) @ 5,250–6,100 rpm | |
Torque | 500 Nm @ 1,800–5,800 rpm | |
Fuel system | High-pressure direct injection (up to 350 bar) | |
Emissions standard | Euro 6d-TEMP | |
Compression ratio | 10.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Single twin-scroll turbo (BorgWarner) | |
Timing system | Double roller chain (primary and secondary) | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 184 kg |
The Mercedes-Benz M 257.920 was used across Mercedes-Benz's W222/W213/W167 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced engine mounts in the W222 and revised exhaust manifolds in the W167-and from 2023 the W223 S-Class adopted the M 256-based M 256H hybrid variant, creating interchange limits. All adaptations are documented in OEM technical bulletins.
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The M 257.920 delivers smooth, responsive performance but early models (2017–2019) are prone to EQ Boost (BAS) and turbocharger issues. Later units (post-2020) with revised components are more durable. Longevity depends heavily on maintenance—consistent oil changes with 0W-40 MB 229.52 oil and attention to hybrid and cooling systems are essential for reliable operation beyond 120,000 km.
Key issues include EQ Boost (BAS) failure, turbocharger bearing wear, ignition coil failures, and cooling system leaks. These are documented in Mercedes-Benz service bulletins. Regular inspection of BAS, turbocharger, and cooling components can prevent major failures and maintain peak performance.
The M 257.920 was used in the W222 S-Class (S 450, 2017–2020), W213 E-Class (E 450, 2017–2023), and W167 GLE-Class (GLE 450, 2018–2023). It was the first inline-six to feature EQ Boost mild hybrid technology. No external licensing or cross-manufacturer applications are documented.
Yes, within limits. ECU remapping can achieve gains of ~20-40 kW due to the engine's robust internals. Performance is best enhanced through exhaust, intake, and intercooler upgrades while preserving reliability. Over-tuning risks damaging the turbocharger and EQ Boost system due to the engine's integrated electrification and thermal loads.
Fuel consumption is moderate for a turbocharged six-cylinder. In the E 450 (W213), typical usage is ~9.8 L/100km (city) and ~7.2 L/100km (highway), or approximately 34 mpg UK combined. Real-world figures vary with driving style, but expect 30–36 mpg (UK) in mixed conditions. The EQ Boost system contributes to improved efficiency in urban driving.
Yes. The M 257.920 is an interference engine. If the timing chain fails or jumps, pistons will contact open valves, resulting in catastrophic internal damage. While the double roller chain design is robust, regular inspection and adherence to maintenance schedules are critical to prevent failure.
Mercedes-Benz specifies 0W-40 oil meeting MB 229.52 standard. Use only high-quality synthetic oils designed for turbocharged petrol engines. Change oil every 15,000 km or annually to ensure proper turbocharger and timing chain lubrication, preventing premature wear under aggressive driving conditions.
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Regulation (EC) No 715/2007
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