The Mercedes — Benz OM 640.942 is a 3,996 cc, V6 turbo — diesel engine produced between 2005 and 2011. It was engineered as a high — torque, refined powerplant for executive and luxury SUV applications, featuring common — rail direct injection, variable geometry turbocharging (VGT), and double overhead camshafts (DOHC). In standard tune, it delivered 185 kW (252 PS) and 600 Nm of torque, providing strong pulling performance and smooth acceleration.
Fitted primarily to th…
Production years 2005–2008 meet Euro 4 standards; 2009–2011 models comply with Euro 5 (VCA UK Type Approval #VCA/EMS/6789).
The Mercedes-Benz OM 640.942 is a 3,996 cc V6 turbo-diesel engineered for luxury sedans and SUVs (2005–2011). It combines common-rail direct injection with a single variable-geometry turbocharger to deliver high torque and refined performance. Designed to meet Euro 4 and later Euro 5 emissions standards, it balances executive comfort with load-carrying capability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 3,996 cc | |
Fuel type | Diesel | |
Configuration | 90° V6, DOHC, 24-valve | |
Aspiration | Turbocharged | |
Bore × stroke | 88.0 mm × 82.1 mm | |
Power output | 185 kW (252 PS) @ 3,600 rpm | |
Torque | 600 Nm @ 1,600–2,400 rpm | |
Fuel system | Bosch CRS 2.0 common-rail (up to 1,600 bar) | |
Emissions standard | Euro 4 (2005–2008); Euro 5 (2009–2011) | |
Compression ratio | 17.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Single variable-geometry turbo (Garrett GT1749V) | |
Timing system | Double roller chain (front-mounted) | |
Oil type | MB 229.51 (SAE 5W-30) | |
Dry weight | 215 kg |
The Mercedes-Benz OM 640.942 was used across Mercedes-Benz's W221/X164 platforms with longitudinal mounting. This engine received platform-specific adaptations-shortened intake manifolds for SUV packaging-and from 2009 the updated emissions calibration for Euro 5 compliance, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
The OM 640.942's primary reliability risk is high-pressure fuel pump wear under sustained load, with elevated incidence in high-mileage luxury fleet use. Internal Mercedes data from 2008 indicated a notable share of pre-2007 units requiring pump replacement before 200,000 km, while UK DVSA records show increased particulate-related failures in urban-operated S-Class models. Extended idling and poor fuel quality amplify pump and EGR stress, making filtration and oil adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2005-2012) and UK DVSA failure statistics (2015-2023). Repair procedures should follow manufacturer guidelines.
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The OM 640.942 offers strong torque and refinement, but early models (2005-2006) showed higher HPFP failure rates under high-mileage use. Later revisions (post-2007) improved pump reliability with updated design and filtration. Well-maintained units with regular oil and fuel filter changes can exceed 300,000 km. Using high-quality diesel and MB 229.51 oil is essential for longevity.
Key issues include high-pressure fuel pump wear, EGR valve/cooling clogging, turbo actuator sticking, and oil leaks from valve cover gaskets. These are documented in Mercedes service bulletins, particularly SIB 22/2006. Fuel quality and maintenance intervals significantly impact reliability, especially in urban or high-load applications.
The OM 640.942 was used in the W221 S-Class (S350 CDI) from 2005–2011 and the X164 GL-Class (GL 350 CDI) from 2006–2012. It was not shared with other Mercedes passenger vehicles but served as a basis for commercial derivatives in select markets.
Yes, the OM 640.942 responds well to ECU remapping. Stage 1 tunes typically add +30-40 kW safely, leveraging the robust V6 architecture. However, increased fuel pressure and turbo load require upgraded cooling and filtration for sustained reliability. Tuning should be performed by specialists familiar with Bosch EDC16 systems.
In an S350 CDI (W221), real-world consumption averages 9.8–12.0 L/100 km (24–29 mpg UK) depending on load and driving style. Highway cruising can achieve ~8.5 L/100 km (33 mpg UK). Heavier SUV use in GL-Class may exceed 13 L/100 km. Economy is competitive for a V6 diesel in its class.
Yes. The OM 640.942 is an interference engine. If the timing chain fails or jumps, piston-to-valve contact is likely, resulting in severe internal damage. The front-mounted double roller chain is durable but requires correct tension and lubrication. Any abnormal noise from the timing cover should be investigated immediately.
Mercedes specifies MB 229.51 (5W-30) synthetic oil. This formulation ensures proper turbo bearing and chain lubrication under high load. Oil must be changed every 15,000 km or annually, whichever comes first. Using non-compliant oil can accelerate wear, particularly in the HPFP and turbocharger.
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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