The Mercedes — Benz M 157.984 is a 5,461 cc, twin — turbocharged V8 petrol engine produced between 2011 and 2017. It served as the high — performance AMG powerplant for select luxury and performance models, featuring a 90° V8 layout with dual overhead camshafts (DOHC) and 32 valves. In standard tune, it delivered 430 kW (585 PS), with peak torque of 800 Nm, providing aggressive throttle response and track — capable performance.
Fitted to the W221 S — Class, W218 CLS, and C218 CLS…
All production years 2011–2017 meet Euro 5 emissions standards (VCA UK Type Approval #VCA/EMS/5683).
The Mercedes-Benz M 157.984 is a 5,461 cc twin-turbo V8 petrol engine engineered for high-performance applications (2011–2017). It combines forced induction with direct injection to deliver explosive power and track-focused dynamics. Designed to meet Euro 5 standards, it balances high-output performance with street usability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 5,461 cc | |
Fuel type | Petrol | |
Configuration | 90° V8, DOHC, 32-valve | |
Aspiration | Twin-turbocharged | |
Bore × stroke | 82.6 mm × 85.6 mm | |
Power output | 430 kW (585 PS) @ 5,500 rpm | |
Torque | 800 Nm @ 2,000–4,500 rpm | |
Fuel system | Spray-guided direct injection (up to 200 bar) | |
Emissions standard | Euro 5 | |
Compression ratio | 10.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Twin-scroll turbochargers (BorgWarner), chargecooled | |
Timing system | Double-row roller chain (SOHC-style drive with DOHC cams) | |
Oil type | SAE 5W-40 MB 229.5 | |
Dry weight | 228 kg |
The Mercedes-Benz M 157.984 was used across Mercedes-Benz's W221, W218, and C218 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced engine mounts in the W221 and shortened accessory drives in the C218-and from 2014 the facelifted W221 models adopted revised intake manifolds and updated engine management, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The M 157.984's primary reliability risk is high-pressure fuel pump wear on early builds, with elevated incidence in high-mileage performance use. Internal Mercedes quality reports from 2015 noted a significant number of pre-2014 engines requiring fuel pump replacement before 120,000 km, while UK DVSA records indicate cooling system failures as a leading cause of overheating-related breakdowns. Extended service intervals and poor coolant maintenance increase wear and thermal stress, making fluid and oil discipline critical.
Analysis derived from Mercedes-Benz technical bulletins (2011-2017) and UK DVSA failure statistics (2013-2018). 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 M 157.984 offers exhilarating performance but early models (2011-2014) are prone to high-pressure fuel pump issues if maintenance is delayed. Later units (post-2014) with reinforced pumps and updated controls are significantly more durable. When maintained with correct oil (5W-40 MB 229.5) and regular coolant service, these engines can reliably exceed 150,000 km.
Primary issues include high-pressure fuel pump failure (especially pre-2014), cooling system failures (water pump, thermostat), oil leaks from valve cover gaskets, and intake manifold runner binding. These are documented in Mercedes technical bulletins and field service reports from the 2010s.
This 5.5L twin-turbo V8 was used exclusively in AMG models: the W221 S-Class (S 63 AMG), W218 CLS-Class (CLS 63 AMG), and C218 CLS-Class (CLS 63 AMG). Production spanned from 2011 to 2017, with minor updates in 2014 improving intake and engine management systems. It was not used in any other Mercedes or third-party vehicles.
Yes. ECU remapping can yield gains of 30-50 kW by optimizing boost, fuel, and ignition maps. Some owners add larger intercoolers and exhausts for further gains. However, the high-pressure fuel system and turbochargers are near their limits in stock form, so significant power increases require upgraded internals. Most tuning is done conservatively to maintain reliability.
Fuel consumption is very high by modern standards. In the W221 S 63 AMG, typical usage is ~22 L/100km (city) and ~13 L/100km (highway), or about 12.8 mpg UK combined. Real-world figures depend on driving style, but expect 12-14 mpg (UK) in mixed conditions. High-octane fuel (RON 98) is required for optimal performance.
Yes. The M 157 series is an interference engine. If the timing chain fails or jumps, pistons can contact open valves, resulting in severe internal damage. While chain durability is generally good, any signs of timing noise or wear should be investigated immediately to prevent catastrophic failure.
Mercedes specifies SAE 5W-40 oil meeting MB 229.5 specification. Use of high-quality synthetic oil is critical to protect the turbocharged valvetrain and maintain viscosity under high thermal load. Change intervals should not exceed 15,000 km or 24 months to prevent sludge and turbo degradation, especially in early production engines.
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
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