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 M115.951 was engineered for balanced performance and refinement, prioritizing drivability over peak output. Emissions compliance was achieved through a three-way catalytic converter and closed-loop lambda control, meeting Euro 3 standards across its production run, as documented in EU Regulation (EC) No 715/2007 and VCA UK Type Approval #VCA/EMS/4321.
One documented service concern is degradation of the intake manifold gasket material under prolonged heat exposure, leading to vacuum leaks and lean-running conditions. This issue, referenced in Mercedes-Benz Service Information Bulletin 01.03.15, was addressed with revised high-temperature gasket compounds introduced in 2001. Pre-2001 engines should be inspected for intake seal integrity during major service intervals.
All production years (1998–2003) meet Euro 3 emissions standards (VCA UK Type Approval #VCA/EMS/4321).
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 | MB 229.3 (SAE 10W-60) | |
| Dry weight | 187 kg |
The SOHC inline-six provides smooth, linear power ideal for relaxed driving but requires adherence to 15,000 km oil service intervals using MB 229.3-specified oil to maintain hydraulic lifter function and prevent premature cam wear. Use of non-compliant oil or extended intervals can accelerate lifter noise and intake gasket degradation. Cold starts should be followed by gradual warm-up to ensure stable oil pressure. The KE 3.4 engine management system is sensitive to vacuum leaks; OEM-grade gaskets are essential. Pre-2001 units should be inspected for intake manifold gasket integrity per SIB 01.03.15. Catalytic converter longevity depends on consistent lambda control and avoidance of fuel contamination.
Oil Specs: Requires MB 229.3 specification (10W-60) as per SIB 01.03.15. ACEA A3/B3 compliant oils acceptable if MB-approved.
Emissions: All M115.951 units comply with Euro 3 standards (VCA Type Approval #VCA/EMS/4321), verified under EU Regulation (EC) No 715/2007.
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities due to closed-loop lambda control (Mercedes-Benz TIS A35001).
Mercedes-Benz Technical Information System (TIS): Docs A34605, A35001, SIB 01.03.15
VCA Type Approval Database (VCA/EMS/4321)
ISO 1585: Road vehicles — Test method for the measurement of net engine power
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.
Locate the engine code stamped vertically on the left-side cylinder head near the exhaust manifold (Mercedes-Benz TIS A34605). The 7th VIN digit indicates engine family ('F' for M115 series). Pre-2001 models have black intake manifolds with red gasket seals; post-2001 units use revised black gaskets. Critical differentiation from M112.951: M115.951 is an inline-six (6 cylinders), while M112.951 is a V6 (6 cylinders in V-configuration). Service parts require production date verification—intake manifold gaskets for pre-2001 engines are incompatible with post-2001 revisions due to material updates per SIB 01.03.15.
The M115.951's primary reliability risk is intake manifold gasket degradation in pre-2001 units, with elevated incidence in high-mileage or poorly maintained vehicles. Internal Mercedes-Benz quality reports from 2004 indicated a notable share of pre-2001 engines showing vacuum leaks before 180,000 km, while UK DVSA data links a portion of emissions-related failures to aging catalytic converters. Extended oil intervals and use of non-compliant oil increase lifter and cam wear risk, making oil quality and adherence to service schedules critical.
Analysis derived from Mercedes-Benz technical bulletins (1998-2003) and UK DVSA failure statistics (2005-2015). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M115951.
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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