The Mercedes — Benz OM648.961 is a 3,996 cc, V8 turbo — diesel engine produced between 2011 and 2018. It features common — rail direct injection, variable geometry turbocharging (VGT), and DOHC 32 — valve configuration. In standard output, it delivers 250 kW (340 PS) and 730 Nm of torque, with applications across luxury sedans and high — performance SUVs.
Fitted to models such as the W221 S — Class, W166 ML — Class, and X166 GL — Class, the OM648.961 was engineered for refined pow…
Production years 2011–2012 meet Euro 5 standards; 2013–2018 models comply with Euro 6 depending on market (VCA UK Type Approval #VCA/EMS/5685).
The Mercedes-Benz OM648.961 is a 3,996 cc V8 turbo-diesel engineered for luxury and performance applications (2011–2018). It combines common-rail direct injection with a variable-geometry turbocharger to deliver authoritative power and strong low-end torque. Designed to meet Euro 5 and Euro 6 emissions standards, it balances performance with efficiency for flagship models.
| Parameter | Value | Source |
|---|---|---|
Displacement | 3,996 cc | |
Fuel type | Diesel | |
Configuration | V8, DOHC, 32-valve | |
Aspiration | Turbocharged | |
Bore × stroke | 88.0 mm × 82.1 mm | |
Power output | 250 kW (340 PS) @ 3,600 rpm | |
Torque | 730 Nm @ 1,600–2,400 rpm | |
Fuel system | Bosch CRS 3.0 common-rail (up to 1,800 bar) | |
Emissions standard | Euro 5 (2011–2012); Euro 6 (2013–2018) | |
Compression ratio | 16.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Single variable-geometry turbo (Garrett GT2260V) | |
Timing system | Dual chain (front-mounted, robust design) | |
Oil type | MB 229.5 (SAE 5W-30) | |
Dry weight | 238 kg |
The Mercedes-Benz OM648.961 was used across Mercedes-Benz's W221/W166/X166 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the W166 and revised cooling circuits in the W221-and from 2013 the updated W221 facelift adopted the OM648.962 variant with CP4 fuel system revisions, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The OM648.961'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 2013 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 (2011-2017) and UK DVSA failure statistics (2012-2020). 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 OM648.961 offers authoritative performance and refinement, but early models (2011-2012) are prone to HPFP failures, especially with poor fuel quality. Later revisions (post-2013) with CP4 pumps improved reliability. Well-maintained units with proper oil changes and quality diesel can exceed 250,000 km. Using MB 229.5 oil and adhering to service intervals is essential for longevity.
Key issues include high-pressure fuel pump failure, EGR valve and cooler clogging, turbo actuator sticking, and oil leaks from valve cover gaskets. These are documented in Mercedes-Benz service bulletins. Fuel quality significantly impacts HPFP and injector life. Regular EGR cleaning and use of OEM-spec oil help mitigate common failures.
This 4.0L V8 diesel was used in the W221 S-Class (S400 CDI), W166 ML-Class (ML400 CDI), and X166 GL-Class (GL400 CDI) from 2011 to 2018. It was phased out in favor of newer OM65x variants. No cross-manufacturer usage is documented for this variant.
Yes, the OM648.961 responds well to ECU remapping. Stage 1 tunes typically add +40-60 kW safely, as the stock turbo and internals handle increased torque. Further gains require upgraded cooling, exhaust, and fuel system components. Tuning should be performed by specialists familiar with Bosch CRS 3.0 systems to avoid fuel pump strain.
In combined driving, the OM648.961 achieves approximately 9.2–10.5 L/100km (31–27 mpg UK). Highway driving can yield as low as 7.8 L/100km (~36 mpg UK), while city use may exceed 12.0 L/100km (~24 mpg UK). Real-world consumption depends on vehicle weight and driving style, but it remains competitive for a 4.0L diesel V8.
Yes. The OM648 series is an interference engine. If the timing chain fails or skips, pistons will contact open valves, resulting in catastrophic internal damage. While the front-mounted dual chain is robust, inspection beyond 200,000 km is advised. Any abnormal noise from the timing cover warrants immediate investigation.
Mercedes-Benz specifies SAE 5W-30 oil meeting MB 229.5 standard. This low-SAPS formulation is essential for DPF and turbo longevity. Oil changes should occur every 15,000 km or annually. Using non-compliant oil can lead to CCV clogging, increased oil consumption, and aftertreatment damage.
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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