The Mercedes-Benz OM 646.961 is a 5,960 cc, inline-six turbo-diesel engine produced between 2006 and 2011. It was engineered as a high-torque powerplant for commercial and luxury applications, featuring common-rail direct injection, variable geometry turbocharging (VGT), and double overhead camshafts (DOHC). In standard tune, it delivered 191 kW (260 PS) and 800 Nm of torque, providing strong pulling performance and smooth cruising refinement.
Fitted primarily to the Vito (W639) and Viano (W639) commercial variants, the OM 646.961 was designed for drivers requiring robust load-carrying capability and long-distance comfort. Emissions compliance was achieved through exhaust gas recirculation (EGR), diesel oxidation catalyst (DOC), and diesel particulate filter (DPF), enabling Euro 4 certification across its production run. Its design emphasized durability in mixed urban and highway environments.
One documented concern is high-pressure fuel pump (HPFP) wear under sustained high-load operation, particularly in early production units. This issue, referenced in Mercedes-Benz Service Information Bulletin 22/2007, was linked to fuel quality sensitivity and inadequate filtration in pre-2008 builds. From 2008 onward, an updated HPFP design and revised ECU calibration were implemented to improve long-term reliability under real-world conditions.
Production years 2006–2011 meet Euro 4 standards (VCA UK Type Approval #VCA/EMS/6793).
The Mercedes-Benz OM 646.961 is a 5,960 cc inline-six turbo-diesel engineered for commercial and luxury MPVs (2006–2011). It combines common-rail direct injection with a single variable-geometry turbocharger to deliver high torque and driving comfort. Designed to meet Euro 4 emissions standards, it balances load-carrying capability with driver comfort.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 5,960 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-6, DOHC, 24-valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 106.0 mm × 112.0 mm | |
| Power output | 191 kW (260 PS) @ 3,200 rpm | |
| Torque | 800 Nm @ 1,400–2,600 rpm | |
| Fuel system | Bosch CRS 2.0 common-rail (up to 1,600 bar) | |
| Emissions standard | Euro 4 | |
| Compression ratio | 17.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Single variable-geometry turbo (Garrett GT2260V) | |
| Timing system | Double roller chain (front-mounted) | |
| Oil type | MB 229.51 (SAE 5W-30) | |
| Dry weight | 325 kg |
The inline-six configuration delivers exceptional low-RPM torque ideal for heavy-duty use, but requires adherence to 15,000 km oil change intervals using MB 229.51 specification oil to maintain chain and turbo longevity. Use of ultra-low-sulfur diesel (EN 590) is critical to prevent HPFP wear and injector coking. Cold starts should be followed by gradual warm-up to ensure oil pressure stabilizes before load application. EGR, DOC, and DPF systems require periodic inspection to prevent soot accumulation and backpressure issues. Post-2008 models benefit from revised fuel pump design and improved ECU calibration per SIB 22/2007.
Oil Specs: Requires MB 229.51 (5W-30) specification (Mercedes-Benz SIB 22/2007). Not compatible with ACEA A/B standards.
Emissions: Euro 4 certification applies to all models (2006–2011) (VCA Type Approval #VCA/EMS/6793).
Power Ratings: Measured under DIN 70020 standards. Output remains consistent across fuel grades meeting EN 590 (Mercedes-Benz TIS Doc. A33510).
Mercedes-Benz Technical Information System (TIS): Docs A32876, A33130, SIB 22/2007
VCA Type Approval Database (VCA/EMS/6793)
SAE International: DIN 70020 Engine Power Test Code
The Mercedes-Benz OM 646.961 was used across Mercedes-Benz's W639 platform with longitudinal mounting. This engine received platform-specific adaptations-shortened intake manifolds for van packaging-and from 2008 the updated emissions calibration for enhanced DPF regeneration, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the left-side cylinder block near the exhaust manifold (Mercedes-Benz TIS A32921). The 8th VIN digit indicates engine type ('M' for OM 646 series). Pre-2008 models have silver valve covers with ribbed timing covers; post-2008 units retain similar styling but feature updated fuel pump calibration. Critical differentiation from OM 642 series: OM 646.961 has larger displacement (5.9L), distinct engine mounting points, and higher torque output. Service parts require production date verification - fuel filters for pre-2008 builds are not compatible with later units due to housing redesign (Mercedes-Benz SIB 22/2007).
The OM 646.961's primary reliability risk is high-pressure fuel pump wear under sustained load, with elevated incidence in commercial fleet use. Internal Mercedes data from 2008 indicated a notable share of pre-2008 units requiring pump replacement before 200,000 km, while UK DVSA records show increased particulate-related failures in urban-operated vans. Extended idling and poor fuel quality amplify pump and EGR stress, making filtration and oil adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2006-2011) and UK DVSA failure statistics (2015-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM646961.
Comprehensive technical documentation and regulatory references
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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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Vehicle Certification Agency (VCA)
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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