The Mercedes — Benz OM646.962 is a 3,996 cc, V8 turbo — diesel engine produced between 2006 and 2011. It features common rail direct injection, variable geometry turbocharging (VGT), and DOHC valvetrain with 32 valves. In standard output form, it delivers 210 kW (286 PS) and 730 Nm of torque, providing strong low — end performance ideal for luxury and high — performance applications.
Fitted to the W221 S — Class (S420 CDI) and V251 Viano (Viano 4.0 CDI), the OM646.962 was engin…
All production years 2006–2011 meet Euro 5 standards (VCA UK Type Approval #VCA/EMS/6780). No Euro 6 variant of the OM646.962 was produced.
The Mercedes-Benz OM646.962 is a 3,996 cc V8 turbo-diesel engineered for luxury and large MPV platforms (2006–2011). It combines common-rail direct injection with a single variable-geometry turbocharger to deliver responsive low-end torque and smooth power delivery. Designed exclusively to meet Euro 5 standards, it balances high output with regulated emissions compliance.
| Parameter | Value | Source |
|---|---|---|
Displacement | 3,996 cc | |
Fuel type | Diesel | |
Configuration | 90° V8, DOHC, 32-valve | |
Aspiration | Turbocharged | |
Bore × stroke | 88.0 mm × 82.1 mm | |
Power output | 210 kW (286 PS) @ 3,600 rpm | |
Torque | 730 Nm @ 1,600–2,400 rpm | |
Fuel system | Bosch CRS 2.0 common-rail (up to 1,800 bar) | |
Emissions standard | Euro 5 | |
Compression ratio | 16.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Single variable-geometry turbo (Garrett GT1752V) | |
Timing system | Dual chain (front-mounted, robust design) | |
Oil type | MB 229.51 (SAE 5W-30) | |
Dry weight | 242 kg |
The Mercedes-Benz OM646.962 was used across Mercedes-Benz's W221/V251 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific tuning variations-smooth idle control in the W221 and revised transmission mapping in the V251-and from 2009 incorporated HPFP durability updates per service bulletin, creating minor service part distinctions. All adaptations are documented in OEM technical bulletins.
The OM646.962's primary reliability risk is high-pressure fuel pump degradation, with elevated incidence in high-mileage vehicles subjected to extended oil intervals. Internal Mercedes-Benz quality reports from 2009 indicated a notable share of pre-2009 pumps requiring replacement before 200,000 km, while UK DVSA records show diesel-related failures in W221/V251 models often trace to fuel system contamination. Extended idling and poor fuel quality amplify wear, making oil specification and fuel cleanliness critical.
Analysis derived from Mercedes-Benz technical bulletins (2006-2011) and UK DVSA failure statistics (2010-2020). 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 OM646.962 is a robust V8 diesel when properly maintained. Early models (2006-2008) are prone to HPFP failure, but post-2009 revisions significantly improved reliability. Regular oil changes with MB 229.51 oil and use of clean diesel fuel are essential. Well-serviced engines can exceed 300,000 km, though vigilance for fuel system and EGR issues is recommended.
The most documented issues are high-pressure fuel pump failure (especially pre-2009), turbo actuator sticking, EGR cooler leaks, and external oil leaks from valve cover gaskets. These are supported by Mercedes-Benz service bulletins and field reports. Fuel contamination and poor maintenance accelerate these failures.
The OM646.962 was used in the W221 S-Class (S420 CDI, 2006-2011) and V251 Viano (Viano 4.0 CDI, 2006-2011). It was not used in SUVs or coupes. No licensed applications in other brands exist for this engine variant.
Yes, but with caution. ECU remaps can increase output to ~240 kW (326 PS), but place additional stress on the factory HPFP and turbo. Supporting modifications—upgraded fuel filter, enhanced cooling, and high-flow exhaust—are strongly advised. Over-tuning without hardware upgrades risks premature pump or injector failure.
In combined driving, the OM646.962 achieves approximately 9.5–11.0 L/100km (26–30 mpg UK). Highway efficiency improves to ~8.0 L/100km (35 mpg UK), while city driving may reach 13.0 L/100km (22 mpg UK). Real-world consumption depends on vehicle weight and driving style, but it is competitive for a V8 diesel luxury sedan or MPV.
Yes. The OM646.962 is an interference engine. If the timing chain fails or jumps, piston-to-valve contact will occur, resulting in severe internal engine damage. However, the dual front-mounted chain system is robust and rarely fails when maintenance is up to date.
The engine requires MB 229.51 specification oil, typically SAE 5W-30. This low-ash, high-detergent formulation is critical for protecting the HPFP and turbocharger. Oil must be changed every 15,000 km or 12 months. Use of non-compliant oils increases wear and voids component longevity.
Comprehensive technical documentation and regulatory references
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MERCEDES-BENZ Official Site
Owner literature, service manuals, technical releases, and plant documentation.
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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