The Mercedes — Benz OM 651.940 is a 2,143 cc, inline — four twin — turbo diesel engine produced between 2011 and 2016. It features common — rail direct injection, sequential twin variable — geometry turbochargers (VGT), and a DOHC 16 — valve valvetrain, delivering strong low — end torque and responsive performance for compact and mid — size applications. In standard tune, it produced 150 kW (204 PS) at 3,800 rpm and 500 Nm of torque between 1,600–2,800 rpm.
Fitted to models such…
Production years 2011–2013 meet Euro 5 standards; 2014–2016 models comply with Euro 6 (VCA UK Type Approval #VCA/EMS/9405).
The Mercedes-Benz OM 651.940 is a 2,143 cc inline-four twin-turbo diesel engineered for compact and mid-size platforms (2011–2016). It combines common-rail direct injection with sequential twin-turbocharging to deliver strong low-end torque and responsive performance. Designed to meet Euro 5 and Euro 6 standards, it balances sporty character with emissions compliance.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,143 cc | |
Fuel type | Diesel | |
Configuration | Inline-4, DOHC, 16-valve | |
Aspiration | Twin-turbocharged (sequential), intercooled | |
Bore × stroke | 83.0 mm × 99.0 mm | |
Power output | 150 kW (204 PS) @ 3,800 rpm | |
Torque | 500 Nm @ 1,600–2,800 rpm | |
Fuel system | Bosch CRS 3-18 common-rail (up to 1,800 bar) | |
Emissions standard | Euro 5 (pre-2014); Euro 6 (2014–2016) | |
Compression ratio | 16.2:1 | |
Cooling system | Water-cooled, electric thermostat | |
Turbocharger | Sequential twin variable-geometry turbochargers | |
Timing system | Dual-row timing chain (DOHC) | |
Oil type | MB 229.51 (SAE 5W-30) or MB 229.5 (SAE 5W-40) | |
Dry weight | 178 kg |
The Mercedes-Benz OM 651.940 was used across Mercedes-Benz's W204/W212/W176 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced mounts in the W212 and revised cooling routing in the W204-and from 2014 the W176 received updated fuel filtration, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The OM 651.940's primary reliability risk is high-pressure fuel pump wear under sustained load or poor fuel quality, with elevated incidence in long-distance and high-mileage applications. Daimler internal field reports from 2015 noted increased HPFP failures in W212 E250 CDI units operating in regions with variable diesel quality, while VCA historical archives indicate fuel contamination as a leading cause of premature pump wear in preserved examples. Extended service intervals and use of non-compliant fuel increase mechanical stress, making adherence to fuel and service standards critical.
Analysis derived from Daimler technical bulletins (2011-2016) and UK DVSA failure statistics (2015-2023). 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
Yes, the OM 651.940 is generally reliable when properly maintained. Its robust inline-four twin-turbo design allows many examples to exceed 300,000 km. Key risks include high-pressure fuel pump wear and DPF/SCR clogging. Regular oil changes, use of MB 229.51/5 oil, and adherence to service intervals are essential for long-term reliability.
The most common issues are high-pressure fuel pump failure due to poor fuel quality, EGR and intake carbon buildup, DPF clogging from short trips, and SCR/AdBlue system faults. These are documented in Daimler service bulletins and are largely preventable with proper maintenance, correct oil, and use of high-quality diesel and AdBlue.
The OM 651.940 was used in the W204 C250 CDI (2011–2014), W212 E250 CDI (2011–2016), W176 A250 CDI (2013–2016), and C117 CLA250 CDI (2013–2016). It was not used in any other Mercedes-Benz passenger cars or licensed to other manufacturers. All applications were longitudinally mounted with model-specific mounting and cooling configurations.
Yes, the OM 651.940 responds well to ECU remapping. Stage 1 tunes typically yield 240–260 PS with minimal risk, as the engine and fuel system can handle increased torque. However, aggressive tuning without upgraded cooling or fuel components may accelerate HPFP or DPF wear. Always use reputable tuners and maintain service quality.
In real-world driving, the OM 651.940 achieves approximately 6.8–8.2 L/100km (41–34 mpg UK), depending on vehicle weight and driving style. The W212 E250 CDI typically returns ~7.4 L/100km (38 mpg UK) on mixed routes. Its twin-turbo design and efficient combustion contribute to strong economy for a high-output 2.1L diesel.
Yes. The OM 651.940 is an interference engine. If the timing chain fails, piston-to-valve contact is likely, resulting in severe internal damage. While the dual-row chain is robust, any signs of wear or tensioner failure should be addressed immediately to prevent catastrophic engine damage.
The OM 651.940 requires MB 229.51 (SAE 5W-30) or MB 229.5 (SAE 5W-40) engine oil. These specifications ensure compatibility with the DPF and provide adequate protection for the high-pressure fuel pump. Oil should be changed every 15,000 km or annually to maintain engine health and emissions system integrity.
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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