The Mercedes-Benz OM668.942 is a 3,996 cc, V8 turbo-diesel engine produced between 2006 and 2011. It was engineered as a high-performance diesel powerplant for luxury and performance applications, featuring common-rail direct injection, variable geometry turbocharging (VGT), and DOHC valvetrain architecture. In standard tune it delivered 210 kW (286 PS) and 700 Nm of torque, providing strong low-end response suitable for high-speed and towing applications.
Fitted primarily to the W221 S-Class (S 420 CDI) and R230 SL-Class (SL 420 CDI), the OM668.942 was designed to deliver refined power and smooth performance in flagship grand tourers. Emissions compliance was achieved through cooled exhaust gas recirculation (EGR), a diesel oxidation catalyst (DOC), and a diesel particulate filter (DPF), meeting Euro 4 standards across all production years. Its 90° V8 layout allowed for longitudinal mounting with balanced weight distribution.
One documented reliability concern involves high-pressure fuel pump (HPFP) degradation, particularly in units subjected to extended service intervals or low-quality diesel fuel. This issue, referenced in Mercedes-Benz Service Bulletin 20/2008, is attributed to wear in the Bosch CP3 pump’s internal cam ring and roller tappets. Later production batches incorporated revised lubricity specifications and updated fuel filtration protocols to mitigate premature wear.
All production years 2006–2011 meet Euro 4 emissions standards (VCA UK Type Approval #VCA/EMS/7900).
The Mercedes-Benz OM668.942 is a 3,996 cc V8 turbo-diesel engineered for full-size luxury vehicles (2006–2011). It combines common-rail direct injection with a single variable-geometry turbocharger to deliver strong low-end torque and smooth power delivery. Designed to meet Euro 4 standards, it balances premium refinement with robust diesel efficiency.
| 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 | 700 Nm @ 1,600–2,400 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 | Dual-row roller chain (front-mounted) | |
| Oil type | MB 229.51 (SAE 5W-30) | |
| Dry weight | 238 kg |
The 90° V8 configuration provides smooth power delivery with inherent balance, but demands strict adherence to 15,000 km oil change intervals using MB 229.51-specified oil to ensure HPFP and chain longevity. The Bosch CRS 2.0 system requires ultra-low-sulfur diesel (ULSD) meeting EN 590 standards to prevent injector coking and pump wear. Cold-start idling should be limited to reduce EGR soot accumulation. Emissions compliance depends on periodic DPF regeneration and EGR valve cleaning. Pre-2008 units are more prone to HPFP failure; post-service bulletin updates include revised fuel filters and lubricity additives.
Oil Specs: Requires MB 229.51 (5W-30) specification (MB SIB 20/2008). Supersedes ACEA B4 standards.
Emissions: Euro 4 certification applies to all models (2006–2011) (VCA Type Approval #VCA/EMS/7900).
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel grades meeting EN 590 (MB TIS Doc. A221-810).
Mercedes-Benz Technical Information System (TIS): Docs A221-801, A221-802, SIB 20/2008
VCA Type Approval Database (VCA/EMS/7900)
SAE International: DIN 70020 Engine Power Measurement Standard
The Mercedes-Benz OM668.942 was used across Mercedes-Benz's W221/R230 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-longer intake manifolds in the W221 and revised exhaust routing in the R230-and from 2009 the facelifted W221 LCI models adopted updated EGR cooling, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine identification number stamped on the right-side cylinder block near the exhaust manifold (MB TIS A221-805). The 8th VIN digit indicates engine type ('V' for OM668 series). Pre-2008 models have silver valve covers with ribbed design; post-2008 units use black valve covers. Critical differentiation from OM668.943: OM668.942 has Bosch CRS 2.0 injection with round ECU connector, while OM668.943 uses piezo injectors with rectangular connector. Service parts require model year verification - HPFP and EGR coolers for pre-2008 models are not interchangeable with later revisions (MB SIB 20/2008).
The OM668.942's primary reliability risk is high-pressure fuel pump wear, with elevated incidence in vehicles using non-compliant diesel or extended oil intervals. Internal Mercedes-Benz field reports from 2009 indicated a significant portion of pre-2008 units required HPFP replacement before 180,000 km, while UK DVSA records show EGR-related faults contribute to emissions failures in urban-driven examples. Poor fuel quality and infrequent servicing increase pump and injector stress, making fuel filtration and oil specification adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2006–2012) and UK DVSA failure statistics (2015–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM668942.
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
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