The Mercedes-Benz OM629.912 is a 3,009 cc, V6 turbo-diesel engine produced between 2005 and 2011. It features common-rail direct injection, variable geometry turbocharging (VGT), and DOHC 24-valve configuration. In standard output, it delivers 150 kW (204 PS) and 500 Nm of torque, with applications across executive and luxury SUV segments.
Fitted to models such as the W211 E-Class, W221 S-Class, and W164 ML-Class, the OM629.912 was engineered for smooth power delivery, low-end torque, and long-distance refinement. Emissions compliance was achieved via exhaust gas recirculation (EGR) and a diesel particulate filter (DPF), enabling Euro 4 certification for early models and Euro 5 compliance for post-2008 builds in key markets.
One documented reliability concern is high-pressure fuel pump (HPFP) degradation under sustained high load, highlighted in Mercedes-Benz Service Bulletin 20/2009. Premature wear is linked to fuel quality and inadequate filtration. From 2008 onward, revised Bosch CP4-based fuel systems with improved filtration were implemented to enhance durability.
Production years 2005–2007 meet Euro 4 standards; 2008–2011 models comply with Euro 5 depending on market (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz OM629.912 is a 3,009 cc V6 turbo-diesel engineered for executive and luxury SUV applications (2005–2011). It combines common-rail direct injection with a variable-geometry turbocharger to deliver refined power and strong low-end torque. Designed to meet Euro 4 and Euro 5 emissions standards, it balances performance with efficiency for long-distance driving.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,009 cc | |
| Fuel type | Diesel | |
| Configuration | V6, DOHC, 24-valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 88.0 mm × 82.1 mm | |
| Power output | 150 kW (204 PS) @ 3,600 rpm | |
| Torque | 500 Nm @ 1,600–2,400 rpm | |
| Fuel system | Bosch CRS 3.0 common-rail (up to 1,800 bar) | |
| Emissions standard | Euro 4 (pre-2008); Euro 5 (2008–2011) | |
| Compression ratio | 16.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Single variable-geometry turbo (Garrett GT1749V) | |
| Timing system | Dual chain (front-mounted, robust design) | |
| Oil type | MB 229.5 (SAE 5W-30) | |
| Dry weight | 198 kg |
The V6 configuration provides smooth, linear power delivery ideal for highway cruising but demands strict adherence to 15,000 km oil change intervals using MB 229.5 specification oil to maintain turbo and HPFP longevity. Use of ultra-low-sulfur diesel (EN 590) is critical to prevent injector and fuel pump wear. Cold starts should be brief; prolonged idling increases EGR and DPF soot loading. Post-2008 models benefit from upgraded CP4 fuel pumps and enhanced filtration. EGR and DPF systems require periodic regeneration and cleaning to prevent limp mode. Timing chains are generally durable but inspection is recommended beyond 200,000 km.
Oil Specs: Requires MB 229.5 specification (Mercedes-Benz SIB 22/2007). Not compatible with ACEA A/B standards.
Emissions: Euro 4 applies to pre-2008 models (VCA Type Approval #VCA/EMS/5678). Euro 5 compliance confirmed for 2008–2011 models in EU markets.
Power Ratings: Measured under DIN 70020. Output maintained across EU and North American variants (Mercedes-Benz TIS Doc. M13510).
Mercedes-Benz Technical Information System (TIS): Docs M12680, M13142, SIB 20/2009, SIB 22/2007
VCA Type Approval Database (VCA/EMS/5678)
ISO 1585:1996 Road vehicles — Test code for net power of internal combustion engines
The Mercedes-Benz OM629.912 was used across Mercedes-Benz's W211/W221/W164 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the W164 and revised cooling circuits in the W221-and from 2008 the updated W211 facelift adopted the OM629.913 variant with CP4 fuel system revisions, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front of the cylinder block near the timing cover (Mercedes-Benz TIS M12890). The 8th VIN digit indicates engine type ('6' for OM629 series). Pre-2008 models have silver valve covers with ribbed plastic covers; post-2008 units use black valve covers. Critical differentiation from OM629.913: Original .912 uses Bosch CP3 HPFP with circular fuel filter housing, while .913 uses CP4 with rectangular housing. Service parts require production date verification - fuel pumps and injectors before 06/2008 are not compatible with later units due to CP4 system integration (Mercedes-Benz SIB 20/2009).
The OM629.912's primary reliability risk is high-pressure fuel pump degradation, with elevated incidence in high-mileage and mixed-use conditions. Internal Mercedes quality reports from 2010 indicated a notable frequency of CP3 pump failures before 180,000 km in non-EU fuel markets, while UK DVSA data links EGR-related faults to urban-driven units. Extended idling and poor fuel quality increase HPFP and injector stress, making fuel filtration and oil interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2007-2012) and UK DVSA failure statistics (2012-2020). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM629912.
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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