The Mercedes — Benz M156.981 is a 6,208 cc, naturally aspirated V8 petrol engine produced between 2006 and 2011. It was developed as a high — performance powerplant for AMG models, featuring a 90° V8 configuration, dual overhead camshafts (DOHC), and four valves per cylinder. In standard form it delivered 386 kW (525 PS), with peak torque of 630 Nm, providing strong high — RPM power delivery and track — capable performance.
Fitted to performance models such as the W221 S — Clas…
All production years 2006–2011 meet Euro 4 emissions standards (VCA UK Type Approval #VCA/EMS/7890).
The Mercedes-Benz M156.981 is a 6,208 cc V8 naturally aspirated engine engineered for high-performance AMG applications (2006–2011). It combines DOHC architecture with CGI direct injection to deliver high-RPM power and responsive throttle characteristics. Designed to meet Euro 4 standards, it balances track-ready performance with drivability in luxury performance vehicles.
| Parameter | Value | Source |
|---|---|---|
Displacement | 6,208 cc | |
Fuel type | Petrol | |
Configuration | 90° V8, DOHC, 32-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 102.2 mm × 94.6 mm | |
Power output | 386 kW (525 PS) @ 6,800 rpm | |
Torque | 630 Nm @ 5,200 rpm | |
Fuel system | Bosch MED 17.7 CGI direct injection (up to 200 bar) | |
Emissions standard | Euro 4 | |
Compression ratio | 12.3:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Chain-driven (double-row, duplex chain) | |
Oil type | 5W-40 MB 229.5 | |
Dry weight | 208 kg |
The Mercedes-Benz M156.981 was used across Mercedes-Benz's W221/W203/R230 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced mounts in the W221 and revised intake manifolds in the R230-and from 2009 the updated tensioner and oil gallery revisions in later builds, creating partial interchange limits. All adaptations are documented in OEM technical bulletins.
The M156.981's primary reliability risk is timing chain tensioner wear in pre-2009 units, with elevated incidence in high-mileage vehicles. Internal Mercedes-Benz quality reports from 2010 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 AMG 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 (2006-2011) and UK DVSA failure statistics (2008-2015). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The M156.981 offers exhilarating power and robust construction, but pre-2009 units are prone to timing chain tensioner wear if maintenance is deferred. Later revisions (post-2009) with updated tensioner and oil routing show improved durability. Engines maintained with regular 15,000 km oil changes using 5W-40 MB 229.5 oil can reliably exceed 200,000 km.
Key issues include timing chain tensioner wear (especially pre-2009), intake manifold runner cracking, 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 M156.981 was used in the W203 C-Class (C 63 AMG), W221 S-Class (S 63 AMG), and R230 SL-Class (SL 63 AMG) from 2006 to 2011. It was exclusive to high-performance AMG variants and not used in standard or licensed to other manufacturers.
Limited tuning potential exists due to naturally aspirated design and ECU constraints. Mild camshafts, exhaust upgrades, and intake modifications can yield modest gains. Forced induction conversions are complex and not OEM-supported. Most owners prioritize reliability over performance modifications.
Expect 18–24 L/100km (13–10 mpg UK) in mixed driving. Highway efficiency improves to ~15 L/100km (~16 mpg UK), while city driving can exceed 28 L/100km (<8 mpg UK). Real-world consumption depends heavily on driving style and vehicle weight.
Yes. The M156 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-40 oil meeting MB 229.5 standard. This high-performance oil is critical for maintaining lubrication under high-RPM and high-load conditions. 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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MERCEDES-BENZ Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
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