The Mercedes — Benz M113.991 is a 5,439 cc, V8 naturally aspirated petrol engine produced between 2001 and 2006. It forms part of the M113 engine family, featuring a 90 — degree V8 configuration, dual overhead camshafts (DOHC), and variable valve timing on the intake (VVT). In standard tune, it delivered 225 kW (306 PS) and 460 Nm of torque, providing strong linear power delivery and smooth refinement.
Fitted to high — performance variants such as the E 55 AMG (W211), CLK 55 AMG…
Production years 2001–2003 meet Euro 3 standards; 2004–2006 models meet Euro 4 standards (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz M113.991 is a 5,439 cc V8 naturally aspirated engine engineered for performance sedans and coupes (2001–2006). It combines sequential multi-port fuel injection with intake-side variable valve timing to deliver high-RPM power and smooth throttle response. Designed to meet Euro 3 and Euro 4 emissions standards, it balances AMG-tuned performance with daily drivability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 5,439 cc | |
Fuel type | Petrol | |
Configuration | 90° V8, DOHC, 32-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 97.0 mm × 92.0 mm | |
Power output | 225 kW (306 PS) @ 5,500 rpm | |
Torque | 460 Nm @ 4,000 rpm | |
Fuel system | Sequential multi-port fuel injection | |
Emissions standard | Euro 3 (pre-2004); Euro 4 (2004–2006) | |
Compression ratio | 10.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | N/A | |
Timing system | Dual-row roller chain (double overhead) | |
Oil type | MB 229.3 (SAE 5W-40) | |
Dry weight | 208 kg |
The Mercedes-Benz M113.991 was used across Mercedes-Benz's W211/C209 platforms with longitudinal mounting and reserved for AMG high-performance applications. This engine received platform-specific adaptations-tuned intake manifolds in the CLK 55 and revised exhaust routing in the E 55-and from 2004 the updated W211 facelift adopted minor ECU recalibrations, creating minor service part differences. All adaptations are documented in OEM technical bulletins.
The M113.991's primary reliability risk is camshaft and follower wear in early production units, with elevated incidence in high-RPM or track use. Internal Mercedes-Benz quality reports from 2005 noted a significant number of pre-2004 engines requiring valvetrain repair before 120,000 km, while UK DVSA data links a portion of high-performance MOT failures to exhaust system degradation in modified examples. Extended oil intervals and low-octane fuel increase wear and combustion stress, making oil quality and service adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2003–2007) and UK DVSA failure statistics (2018–2023). 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 M113.991 offers strong performance and smooth operation, but early models (2001–2003) are prone to camshaft and follower wear. Later units (post-2004) benefit from improved oil flow and materials, enhancing durability. Consistent maintenance, use of MB 229.3 oil, and adherence to 15,000 km service intervals are essential for long-term reliability.
Key issues include camshaft and follower wear (especially pre-2004), intake manifold flap failure, cooling system leaks, and ignition coil degradation. These are documented in Mercedes-Benz service bulletins and technical reports. Preventative maintenance significantly reduces failure risk.
The M113.991 was used exclusively in AMG-tuned models: the E 55 AMG (W211), CLK 55 AMG (C209), and SLK 55 AMG (R171), produced between 2001 and 2006. It replaced the M113.973 and was succeeded by the supercharged M113.983.
Limited tuning potential exists due to its naturally aspirated design. ECU remaps offer minor gains (~10–15 kW), but significant power increases require forced induction. Some enthusiasts add supercharger kits, though this requires extensive modification. Stock internals are robust but not designed for high boost.
Moderate for a high-performance V8. Official figures show ~13.5 L/100km (city) and ~7.8 L/100km (highway). Real-world consumption typically ranges 11–15 L/100km depending on driving style. Expect 20–25 mpg (UK) under mixed conditions. RON 98 fuel is recommended for optimal performance.
Yes. The M113.991 is an interference engine. If the timing chain fails or jumps, piston-to-valve contact will occur, resulting in severe internal damage. The dual-row roller chain is durable, but proper maintenance and oil quality are essential to prevent catastrophic failure.
Mercedes-Benz specifies SAE 5W-40 oil meeting MB 229.3 standard. Use only high-quality synthetic oil designed for high-performance petrol engines and change every 15,000 km or annually. Proper lubrication is critical to prevent camshaft and follower wear, especially in early production units.
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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