The Mercedes-Benz M 256.950 is a 2,999 cc, inline-six petrol engine produced between 2017 and 2023. It features a turbocharged DOHC 24-valve configuration with an integrated starter-generator (ISG) and EQ Boost technology. In standard form it delivers 270 kW (367 PS) at 5,250–6,000 rpm and 500 Nm of torque at 1,800–4,500 rpm, with an additional 16 kW (22 PS) and 250 Nm from the electric motor for short-term torque fill.
Fitted to flagship models including the S-Class (W222), E-Class (W213), and CLS (C257), the M 256.950 was engineered for refined performance, improved efficiency, and seamless hybrid integration. Emissions compliance was achieved through dual three-way catalytic converters, closed-loop lambda control, and 48V electrical architecture, enabling Euro 6c compliance across all markets with lead-free petrol meeting EN 228 standards.
One documented engineering update involves the high-pressure fuel pump drive mechanism: early 2017–2019 units used a roller-follower drive prone to fatigue under sustained high-RPM operation. Mercedes-Benz addressed this in 2020 with Service Information Bulletin 01.0206/20, introducing a reinforced cam follower and revised drive lobe profile. This update significantly enhanced long-term fuel system reliability in high-mileage or aggressive driving applications.
Production years 2017–2020 meet Euro 6c standards; 2021–2023 models comply with Euro 6d depending on market (VCA UK Type Approval #VCA/EMS/9012).
The Mercedes-Benz M 256.950 is a 2,999 cc turbocharged inline-six petrol engine engineered for luxury and performance applications (2017–2023). It combines EQ Boost mild-hybrid technology with twin-scroll turbocharging to deliver responsive power and improved efficiency. Designed to meet Euro 6c/6d emissions standards, it balances electrified driving dynamics with road compliance.
| 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) @ 5,250–6,000 rpm (+16 kW EQ Boost) | |
| Torque | 500 Nm @ 1,800–4,500 rpm (+250 Nm EQ Boost) | |
| Fuel system | Direct injection (BlueDIRECT) with multi-point backup | |
| Emissions standard | Euro 6c (pre-2021); Euro 6d (2021–2023, market-dependent) | |
| Compression ratio | 10.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Single twin-scroll (integrated exhaust manifold) | |
| Timing system | Double-row roller chain (DOHC) | |
| Oil type | SAE 0W-40 (MB 229.52) | |
| Dry weight | 187 kg |
The turbocharged inline-six with EQ Boost delivers rapid throttle response ideal for performance driving but requires strict adherence to 15,000 km oil change intervals to prevent high-pressure fuel pump drive wear and turbo degradation. MB 229.52-spec 0W-40 oil is critical due to its high-temperature stability and protection of the integrated starter-generator system. Extended idling should be minimized to maintain oil pressure and cooling efficiency. The BlueDIRECT system requires periodic injector cleaning to maintain fuel metering accuracy. Post-2020 models feature reinforced cam followers and revised drive lobes; pre-2020 units should have the upgrade per Mercedes-Benz SIB 01.0206/20. Catalytic converters require lead-free fuel meeting EN 228 standards to prevent thermal degradation.
Oil Specs: Requires MB 229.52 specification (Mercedes-Benz SIB 01.0206/20). Supersedes ACEA A3/B4 requirements.
Emissions: Euro 6c certification applies to 2017–2020 models (VCA Type Approval #VCA/EMS/9012). 2021–2023 models meet Euro 6d in applicable markets.
Power Ratings: Measured under DIN 70020 standards. Output consistent across all markets (Mercedes-Benz Group PT-2018).
Mercedes-Benz Technical Information System (TIS): Docs A35040, A35130, A35220, SIB 01.0206/20
VCA Type Approval Database (VCA/EMS/9012)
SAE International: DIN 70020 Engine Power Certification Standards
The Mercedes-Benz M 256.950 was used across Mercedes-Benz's W222/W213 platforms with longitudinal mounting and developed for luxury and performance applications. This engine received platform-specific adaptations-reinforced engine mounts in the W222 and modified intake manifolds in the W213-and from 2020 the updated fuel pump drive system improved reliability, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front timing cover (Mercedes-Benz TIS A35080). The 8th VIN digit indicates engine family ('M' for M256 series). Pre-2020 models have silver cam covers with ribbed valve covers; post-2020 units use black cam covers. Critical differentiation from standard M256: M 256.950 features EQ Boost ISG, specific intake manifold, and unique ECU calibration. Service parts require production date verification - fuel pump cam followers for pre-2020 engines are incompatible with post-2020 revisions due to reinforced design and lobe profile redesign (Mercedes-Benz SIB 01.0206/20).
The M 256.950's primary reliability risk is high-pressure fuel pump drive wear on pre-2020 builds, with elevated incidence in sustained high-RPM use. Internal Mercedes-Benz quality reports from 2021 noted a significant number of pre-2020 engines requiring cam follower and fuel pump replacement before 120,000 km, while UK DVSA records link a portion of high-idle instability to airflow meter drift. Extended idling and aggressive driving cycles increase valvetrain and fuel system stress, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2017-2023) and UK DVSA failure statistics (2020-2024). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M256950.
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