The Mercedes — Benz OM656.940 is a 2,925 cc, inline — six turbo — diesel engine produced between 2017 and 2023. It features common — rail direct injection, variable geometry turbocharging (VGT), and DOHC 24 — valve configuration. In standard output, it delivers 230 kW (313 PS) and 700 Nm of torque, with applications across executive sedans and luxury SUVs.
Fitted to models such as the W213 E — Class, W222 S — Class, and W167 GLS — Class, the OM656.940 was engineered for smooth pow…
All production years (2017–2023) comply with Euro 6d-TEMP and Euro 6d standards depending on market and model year .
The Mercedes-Benz OM656.940 is a 2,925 cc inline-six turbo-diesel engineered for executive and luxury applications (2017–2023). It combines common-rail direct injection with a variable-geometry turbocharger to deliver authoritative power and strong low-end torque. Designed to meet Euro 6 emissions standards, it balances performance with efficiency and long-distance refinement.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,925 cc | |
Fuel type | Diesel | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Turbocharged | |
Bore × stroke | 83.0 mm × 94.0 mm | |
Power output | 230 kW (313 PS) @ 3,800 rpm | |
Torque | 700 Nm @ 1,200–3,200 rpm | |
Fuel system | Bosch CRS 3.0 common-rail (up to 1,800 bar) | |
Emissions standard | Euro 6 (2017–2023) | |
Compression ratio | 15.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Single variable-geometry turbo (Garrett GT2060V) | |
Timing system | Dual chain (front-mounted, robust design) | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 198 kg |
The Mercedes-Benz OM656.940 was used across Mercedes-Benz's W213/W222/W167 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the W167 and revised cooling circuits in the W222-and from 2019 the updated W213 facelift adopted the OM656.941 variant with CP4 fuel system revisions, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Engine Finders UK Ltd, which operates EngineCode.uk, can pass your enquiry to engine suppliers in the UK. The service is for vehicles in the United Kingdom, with UK delivery or fitting. This is a commercially connected service, and sending an enquiry does not confirm diagnosis or compatibility.
Diagnostic reminder: If a technician has recommended replacing the engine, you can send an enquiry to engine suppliers in the UK. Confirm the diagnosis first: an engine-code record does not diagnose a fault.
Field reports and technical service bulletins highlight component wear patterns under high-load operation. Adherence to manufacturer service intervals and approved fluid specifications is critical for long-term reliability.
Analysis derived from manufacturer technical service bulletins and industry workshop records. 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 OM656.940 offers smooth performance and strong torque, but early models (2017-2018) are prone to HPFP failures, especially with poor fuel quality. Later revisions (post-2019) with CP4 pumps improved reliability. Well-maintained units with proper oil changes and quality diesel can exceed 250,000 km. Using MB 229.52 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 3.0L inline-six diesel was used in the W213 E-Class (E350d), W222 S-Class (S350d), and W167 GLS-Class (GLS350d) from 2017 to 2023. It was phased out in favor of the OM656.942 in later model years. No cross-manufacturer usage is documented for this variant.
Aftermarket ECU tuning is common on the OM656940 platform, but increasing boost or altering engine parameters accelerates component wear, impacts emissions compliance, and may void vehicle warranties. Any modifications should be evaluated carefully by a qualified specialist.
In combined driving, the OM656.940 achieves approximately 7.0–7.8 L/100km (40–36 mpg UK). Highway driving can yield as low as 6.2 L/100km (~45 mpg UK), while city use may exceed 8.6 L/100km (~33 mpg UK). Real-world consumption depends on vehicle weight and driving style, but it remains competitive for a 3.0L diesel inline-six.
Yes. The OM656 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 0W-30 oil meeting MB 229.52 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
EngineCode.uk is operated by Engine Finders UK Ltd. It provides engine-reference information and an optional commercial enquiry service. It is not an official manufacturer website. Check the record's sources and confirm vehicle-specific details before relying on it for parts, repairs or replacement.
Our editorial standard prioritises relevant manufacturer documentation and official regulatory sources. The sources and verification status for a record should be checked alongside the data.
A statement is not verified merely because a source is listed. Where supporting evidence is missing or conflicting, the record should identify that limitation. Please report unsupported or inconsistent information.
Transparency in gaps
A missing or unverified value does not mean the manufacturer has withheld it. We distinguish information not yet verified, information not available to us, and information explicitly not disclosed by the source.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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.
Records are subject to review and correction. Source links, dates and verification notes should be read with the technical information. Our Editorial and Sourcing Policy explains our standards and review process.
Found an error or missing source? Report a problem with this page. Include the field or statement concerned and a supporting source if available. You can also email corrections@enginecode.uk.
Copyright and permissions
Images and other material may be protected by copyright. Attribution does not by itself grant permission to reuse material. If you believe material on this site infringes your rights, contact copyrights@enginecode.uk with the page URL and details of your claim. We will review the material and take appropriate action.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
Our Privacy Policy explains how Engine Finders UK Ltd uses information from visits, vehicle lookups, enquiries and messages. Our Cookie Policy explains cookies and similar technologies and how to change your choices.
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.
Ownership and commercial services
EngineCode.uk is owned and operated by Engine Finders UK Ltd. Alongside our reference content, we offer an optional replacement-engine enquiry service through Engine Finders and may identify relevant services provided by businesses connected with us. These commercial connections are disclosed. Using an enquiry service is not required to read our reference content.
Engine Finders UK Ltd operates this website. Our optional enquiry service has a commercial purpose. Our Ownership and Commercial Disclosure explains the relationship between the reference website and that service. Participating suppliers pay a fee or subscription to participate on the network and receive quote requests.
Use this record as a starting point for identification. Specifications and vehicle applications may contain errors or omissions. Confirm the exact engine variant and compatibility using vehicle-specific documentation and a qualified supplier or technician.
All external links open in new tabs. Please verify current availability of resources.