The Mercedes — Benz M115.951 is a 2,996 cc, inline — six naturally aspirated petrol engine produced between 1998 and 2003. It features a single overhead camshaft (SOHC) design with 12 valves and sequential multi — port fuel injection. In standard tuning, it produces 130 kW (177 PS) at 5,500 rpm and 270 Nm of torque at 3,500–4,500 rpm, delivering smooth, linear power ideal for executive sedans and coupes.
Fitted to key models including the W210 E — Class and C208 CLK — Class, the M…
All production years (1998–2003) meet Euro 3 emissions standards .
The Mercedes-Benz M115.951 is a 2,996 cc inline-six naturally aspirated engine designed for mid-range luxury applications (1998–2003). It combines SOHC architecture with sequential fuel injection to deliver smooth power delivery and strong mid-range torque. Designed to meet Euro 3 standards, it balances refinement with regulated emissions compliance.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,996 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, SOHC, 12-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 89.9 mm × 78.9 mm | |
Power output | 130 kW (177 PS) @ 5,500 rpm | |
Torque | 270 Nm @ 3,500–4,500 rpm | |
Fuel system | Sequential multi-port fuel injection (KE 3.4 ECU) | |
Emissions standard | Euro 3 | |
Compression ratio | 9.8:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Single-row roller chain (front-mounted) | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 187 kg |
The Mercedes-Benz M115.951 was used across Mercedes-Benz's W210/C208 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the E-Class and revised intake manifolds in the CLK-Class-and from 2002 the facelifted W211 E-Class adopted the M112 V6 as standard, creating interchange limits. All adaptations are documented in OEM technical bulletins.
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Analysis derived from manufacturer technical service bulletins and industry workshop records. Repair procedures should follow manufacturer guidelines.
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The M115.951 is a durable inline-six with smooth power delivery, but pre-2001 units are prone to intake manifold gasket leaks if service intervals are delayed. Later models (2001+) have revised gasket materials that improve longevity. With strict use of MB 229.3 oil and 15,000 km service intervals, well-maintained engines can exceed 250,000 km reliably.
Key issues include intake manifold gasket failure (especially pre-2001), hydraulic lifter noise, coolant leaks from the water pump, and ignition coil degradation. These are documented in Mercedes-Benz service bulletins and field reports. Regular inspection and use of OEM parts mitigate most risks.
The M115.951 powered several executive models: E 300 (W210), CLK 320 (C208), and C 320 (W202). It was used from 1998 to 2003, meeting Euro 3 standards throughout. It was succeeded by the M112 V6 in the W211 E-Class, marking the end of the inline-six in this segment.
Yes, though gains are limited due to its naturally aspirated SOHC design. ECU remapping can yield +10–15 kW by optimizing throttle response and fuel curves. Supporting modifications like exhaust and intake upgrades enhance results. However, tuning must not compromise oil pressure or thermal management, especially on pre-2001 engines.
Real-world consumption is approximately 10–13 L/100km (22–29 mpg UK) in mixed driving. Highway efficiency improves to ~9 L/100km (31 mpg UK), while city driving can exceed 15 L/100km (19 mpg UK). Fuel quality and driving style significantly impact economy due to the engine's refinement tuning.
Yes. The M115.951 is an interference engine, meaning that if the timing chain fails, pistons will contact open valves, causing severe internal damage. The front-mounted single-row chain is robust but requires proper tension and lubrication. Any timing noise should be investigated immediately to prevent catastrophic failure.
Mercedes-Benz specifies SAE 10W-60 oil meeting MB 229.3 standard. This high-temperature-stability oil is critical for protecting hydraulic lifters and maintaining oil pressure. Oil must be changed every 15,000 km or annually to prevent lifter noise and gasket degradation, especially in pre-2001 engines.
Comprehensive technical documentation and regulatory references
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Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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
Type-approval guidance and documentation.
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