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…
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 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.
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.
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The M 256.950 delivers smooth power and modern refinement, but early models (2017–2019) had reliability concerns, especially high-pressure fuel pump drive wear. Later revisions (post-2020) improved durability with reinforced cam followers and revised drive profiles, so well-maintained examples can be robust. Regular servicing and using correct oil (0W-40 MB 229.52) greatly aid longevity, especially in high-RPM applications.
The biggest issues are fuel pump drive wear (leading to whining or failure), airflow meter drift causing idle instability, and intake vacuum leaks. Other concerns include oil leaks from gaskets and occasional throttle body carbon buildup. These are documented in Mercedes-Benz service bulletins and workshop records. The 2020 SIB 01.0206/20 update is critical for long-term reliability.
This 3.0L turbo inline-six was used in several luxury Mercedes-Benz models from 2017 to 2023. It powered the S 450 (W222), E 450 (W213), CLS 450 (C257), and GLE 450 (W167). All units were Euro 6c/6d compliant and featured EQ Boost mild-hybrid technology. It replaced the M276 V6 and is distinct from the M256.980 used in AMG models.
Yes, the M 256.950 is moderately tunable. ECU remaps can yield +30–50 kW by optimizing boost, fuel, and ignition maps, with supporting mods (intercooler, exhaust) enabling further gains. The EQ Boost system can be reprogrammed for extended torque fill. However, over-tuning risks fuel pump and turbo longevity. Most owners preserve originality, but aftermarket tuning is available.
Fuel consumption is moderate due to engine size and vehicle weight. In an E 450 (W213), typical usage is ~9.5 L/100 km (city) and ~7.2 L/100 km (highway), or about 30–40 mpg UK. Real-world figures depend on driving style, but expect 28–36 mpg (UK) on mixed roads for a healthy M 256.950.
Yes. The M 256 series is an interference engine. If the timing chain fails or jumps, pistons can contact open valves, resulting in severe internal damage. That's why chain maintenance and oil system integrity are critical—any abnormal noise should be investigated immediately.
Mercedes-Benz specifies SAE 0W-40 oil meeting MB 229.52 specification. Always use a high-quality synthetic oil suitable for turbocharged petrol engines with 48V systems and change it every 15,000 km or annually to ensure proper component lubrication and prevent wear.
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