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 delivery.
Fitted to models such as the W222 S-Class, W205 C-Class, and W213 E-Class (in 450 variants), the M256.920 was engineered for refined performance and improved fuel economy. It featured Bosch ME 17.8.10 engine management with direct fuel injection (CGI), enabling precise air-fuel control and reduced emissions. Emissions compliance was achieved through close-coupled and underfloor catalytic converters, allowing the engine to meet Euro 6d-TEMP standards across its production run.
One documented concern is premature wear of the timing chain tensioner, which can lead to noise and potential timing misalignment. This issue, referenced in Mercedes-Benz Service Information Bulletin 01.01.182, is linked to oil starvation under sustained high-load operation. In 2020, an updated tensioner design and revised oil gallery routing were introduced to improve lubrication and reduce failure incidence.
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 turbocharged inline-six provides strong low-end torque ideal for performance driving but requires strict adherence to 15,000 km oil change intervals using 5W-30 MB 229.5 specification to prevent timing chain tensioner wear and turbocharger degradation. Use of non-compliant oils accelerates wear in high-load conditions. The Bosch ME 17.8.10 system requires periodic adaptation resets and injector cleaning to maintain throttle response. Pre-2020 engines should have tensioner and guide rail inspected per SIB 01.01.182; later units benefit from improved oil routing. Cooling system integrity is critical due to compact engine bay packaging—inspect thermostat, hoses, and radiator regularly to prevent overheating. CGI injectors are sensitive to fuel quality; only premium unleaded petrol meeting EN 228 should be used.
Oil Specs: Requires MB 229.5 5W-30 (Mercedes-Benz SIB 01.01.182). Supersedes ACEA A5/B5.
Emissions: Euro 6d-TEMP certification applies to all models (2017–2023) (VCA Type Approval #VCA/EMS/7894).
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities (Mercedes-Benz TIS Doc. A37510).
Mercedes-Benz Technical Information System (TIS): Docs A37510, A37550, SIB 01.01.182
VCA Type Approval Database (VCA/EMS/7894)
ISO 1585: Road vehicles — Engine test code — Net power
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.
Locate the engine code stamped vertically on the right-side cylinder block near the oil filter housing (Mercedes-Benz TIS A37510). The 8th VIN digit indicates engine type ('M' for M256 series). Pre-2020 engines have silver cam covers with "M256" branding; post-2020 units use black cam covers with revised tensioner housings. Critical differentiation from M276: M256.920 features EQ Boost 48V system and twin-scroll turbo, while M276 uses side-mounted turbo and no hybrid integration. Service parts require model-year verification—tensioners and timing kits for pre-2020 engines are not interchangeable with later revisions due to oil feed and guide updates (Mercedes-Benz SIB 01.01.182).
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.
Find answers to most commonly asked questions about MERCEDES-BENZ M256920.
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