The Mercedes-Benz OM668.940 is a 5,980 cc, V8 twin-turbo diesel engine produced between 2012 and 2019 as part of the company's high-performance diesel engine family. It features high-pressure common-rail injection (up to 2,000 bar), sequential twin variable-geometry turbochargers (VGT), and dual overhead camshafts (DOHC) with four valves per cylinder. In standard tune, it delivers 325 kW (442 PS), with peak torque of 1,000 Nm, providing exceptional low-end pulling power ideal for luxury and performance SUV applications.
Fitted to models including the GL-Class (X166), S-Class (V222), and G-Class (W463), the OM668.940 was engineered for effortless refinement and commanding performance in flagship platforms. Emissions compliance is achieved through cooled exhaust gas recirculation (EGR), a diesel particulate filter (DPF), and selective catalytic reduction (SCR) with AdBlue injection, enabling Euro 6 compliance across its production run.
One documented reliability concern involves high-pressure fuel pump (HPFP) wear due to internal degradation, which can result in reduced rail pressure and misfires. This issue, referenced in Daimler Service Information Bulletin 205076/2014, is primarily observed in units exceeding 200,000 km. From 2015, revised HPFP calibration and improved lubricity requirements were implemented to extend service life.
All production years 2012–2019 meet Euro 6 emissions standards (VCA UK Type Approval #VCA/EMS/8891).
The Mercedes-Benz OM668.940 is a 5,980 cc V8 twin-turbo diesel engineered for luxury sedan and SUV applications (2012–2019). It combines common-rail direct injection with sequential twin variable-geometry turbochargers to deliver refined power delivery and immense torque. Designed to meet Euro 6 standards, it balances performance with emissions control in premium vehicle segments.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 5,980 cc | |
| Fuel type | Diesel | |
| Configuration | V8, DOHC, 32-valve | |
| Aspiration | Twin-turbocharged (sequential VGT) | |
| Bore × stroke | 88.0 mm × 97.0 mm | |
| Power output | 325 kW (442 PS) @ 3,600–4,400 rpm | |
| Torque | 1,000 Nm @ 1,600–2,400 rpm | |
| Fuel system | Bosch CRS 3.0 common-rail (up to 2,000 bar) | |
| Emissions standard | Euro 6 | |
| Compression ratio | 15.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Sequential twin variable-geometry turbos (BorgWarner) | |
| Timing system | Chain-driven (double-row primary, secondary chains) | |
| Oil type | MB 229.51 (SAE 5W-30) | |
| Dry weight | 385 kg |
The OM668.940 delivers exceptional, refined performance ideal for high-load driving but requires strict adherence to 15,000 km oil change intervals using MB 229.51 oil to maintain fuel pump and turbocharger longevity. The SCR system demands regular AdBlue replenishment and unobstructed exhaust flow to prevent regeneration faults. Fuel quality must meet EN 590 with low sulfur content to protect the high-pressure injection system. Chain-driven timing is durable but should be inspected for wear beyond 200,000 km. Post-2015 models feature revised HPFP calibration per Daimler SIB 205076/2014, reducing failure risk. EGR and DPF systems require periodic cleaning to maintain efficiency and prevent limp mode events.
Oil Specs: Requires MB 229.51 specification (5W-30) (Daimler SIB 205076/2014). Compatible with ACEA C3 standards.
Emissions: Euro 6 certification applies to all 2012–2019 models (VCA Type Approval #VCA/EMS/8891).
Power Ratings: Measured under ECE R85 standards. Output maintained across EU markets with EN 590 diesel (Daimler TIS Doc. A44077).
Daimler Technical Information System (TIS): Docs A44077, SIB 205076/2014
VCA Type Approval Database (VCA/EMS/8891)
European Commission Regulation (EU) 2017/1151
The Mercedes-Benz OM668.940 was used across Mercedes-Benz's X166/V222/W463 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced mounts in the G-Class and revised cooling in the S-Class-and from 2015 the facelifted GL-Class models adopted updated SCR calibration, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine identification number stamped horizontally on the front right-side engine block near the timing cover (Daimler TIS A44077). The 8th VIN digit indicates engine type ('8' for OM668 series). Pre-2015 models have silver fuel rail covers; post-2015 units use black covers with updated sensors. Critical differentiation from OM656.980: OM668.940 has a V8 layout with twin VGT turbos, while OM656.980 uses an inline-six configuration. Service parts require production date verification—HPFP units before 06/2015 are not interchangeable with later versions due to internal recalibration (Daimler SIB 205076/2014).
The OM668.940's primary reliability risk is high-pressure fuel pump wear, with elevated incidence in vehicles exceeding 200,000 km. Daimler internal field reports from 2017 indicated a notable frequency of HPFP breakdowns in pre-2015 units, while UK DVSA data links a significant share of emissions-related MOT failures to DPF saturation in urban-driven luxury SUVs. Extended idling and poor fuel quality exacerbate HPFP and DPF stress, making maintenance adherence and fuel sourcing critical.
Analysis derived from Daimler technical bulletins (2012–2019) and UK DVSA failure statistics (2015–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM668940.
Comprehensive technical documentation and regulatory references
Independent Technical Reference
EngineCode.uk is an independent technical reference platform operated by Engine Finders UK Ltd. We are not affiliated with MERCEDES-BENZ or any other manufacturer. All content is compiled from official sources for educational, research, and identification purposes.
Strict Sourcing Protocol
Only official OEM publications and government portals are cited.
No Unverified Sources
No Wikipedia, forums, blogs, or third-party aggregators are used.
Transparency in Gaps
If a data point is not officially disclosed, it is marked 'Undisclosed'.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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.
Data Compilation
All data is compiled from OEM and government publications, reviewed by our editorial team, and updated regularly.
Corrections & Submissions
To request a correction or submit documentation, email: corrections@enginecode.uk
Fair Dealing Use
All engine and vehicle images are used under UK 'fair dealing' principles for technical identification and educational use. Rights remain with their respective owners.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
GDPR Compliance
EngineCode.uk complies with UK GDPR. We do not collect personal data unless explicitly provided.
Data Requests
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
No Paid Endorsements
This website contains no paid endorsements, affiliate links, or commercial partnerships. We do not sell parts or services.
Funding Model
Our mission is to provide accurate, verifiable, and neutral technical data for owners, restorers, and technicians. This site is self-funded.
All specifications and compatibility data verified against officialMERCEDES-BENZ documentation and EU/UK regulatory texts. Where official data is unavailable, entries are marked “Undisclosed“ .
All external links open in new tabs. Please verify current availability of resources.
