The Mercedes — Benz M256.920 is a 2,999 cc, inline — six turbocharged petrol engine produced between 2017 and 2023. It was developed as a modular, high — efficiency powerplant for luxury and performance applications, featuring a DOHC 24 — valve layout, twin — scroll turbocharging, and integrated 48V mild — hybrid system (EQ Boost). In standard configuration it delivered 270 kW (367 PS), with peak torque of 500 Nm, providing strong low — end response and smooth high — RPM power…
All production years 2017–2023 meet Euro 6d-TEMP emissions standards (VCA UK Type Approval #VCA/EMS/7894).
The Mercedes-Benz M256.920 is a 2,999 cc inline-six turbocharged engine engineered for mid-to-flagship luxury platforms (2017–2023). It combines DOHC architecture with CGI direct injection, twin-scroll turbocharging, and EQ Boost 48V mild-hybrid technology to deliver responsive low-end torque and refined power delivery. Designed to meet Euro 6d-TEMP standards, it balances performance with improved efficiency over previous V8 applications.
| 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 | |
Torque | 500 Nm @ 1,600–4,000 rpm | |
Fuel system | Bosch ME 17.8.10 CGI direct injection (up to 200 bar) | |
Emissions standard | Euro 6d-TEMP | |
Compression ratio | 10.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Single twin-scroll turbocharger (BorgWarner) | |
Timing system | Chain-driven (double-row, duplex chain) | |
Oil type | 5W-30 MB 229.5 | |
Dry weight | 187 kg |
The Mercedes-Benz M256.920 was used across Mercedes-Benz's W222/W205/W213 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced mounts in the W222 and revised intake manifolds in the W213-and from 2020 the updated tensioner and oil gallery revisions in later builds, creating partial interchange limits. All adaptations are documented in OEM technical bulletins.
The M256.920's primary reliability risk is timing chain tensioner wear in pre-2020 units, with elevated incidence in high-mileage vehicles. Internal Mercedes-Benz quality reports from 2021 noted a significant number of early engines requiring tensioner replacement before 120,000 km, while UK DVSA MOT records show elevated engine-related failures in hybrid-equipped models with deferred maintenance. Extended oil intervals and use of non-compliant oils increase wear rates, making oil quality and schedule adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2017-2023) and UK DVSA failure statistics (2019-2024). Repair procedures should follow manufacturer guidelines.
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The M256.920 offers smooth power and solid construction, but pre-2020 units are prone to timing chain tensioner wear if maintenance is deferred. Later revisions (post-2020) with updated tensioner and oil routing show improved durability. Engines maintained with regular 15,000 km oil changes using 5W-30 MB 229.5 oil can reliably exceed 200,000 km.
Key issues include timing chain tensioner wear (especially pre-2020), intake carbon buildup, ECU communication faults, and cooling system leaks. These are documented in Mercedes-Benz service bulletins and technical forums. Regular inspection and use of correct fluids mitigate most risks.
The M256.920 was used in the W205 C-Class (C 450), W213 E-Class (E 450), and W222 S-Class (S 450) from 2017 to 2023. It was exclusive to mid-to-high-end inline-six petrol variants and not used in performance AMG or licensed to other manufacturers.
Yes. The turbocharged inline-six responds well to ECU remapping. Stage 1 tunes typically yield +40–60 kW safely. Upgraded turbos, intercoolers, and exhaust systems allow further gains. However, fuel pump and injector limits must be considered. Most owners balance performance with reliability, avoiding excessive over-boosting.
Expect 8.5–11.0 L/100km (33–26 mpg UK) in mixed driving. Highway efficiency improves to ~7.5 L/100km (~38 mpg UK), while city driving can reach 13.0 L/100km (~22 mpg UK). Real-world consumption depends heavily on driving style and vehicle weight.
Yes. The M256 series is an interference engine. If the timing chain fails, pistons can contact open valves, resulting in catastrophic engine damage. Regular inspection of the duplex chain and tensioners is essential to prevent failure.
Mercedes-Benz specifies 5W-30 oil meeting MB 229.5 standard. This viscosity ensures proper lubrication of the timing chain system. Oil changes should occur every 15,000 km or annually to prevent tensioner and camshaft wear.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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