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 as the W204 C250 CDI, W212 E250 CDI, and W176 A250 CDI, the OM 651.940 was engineered for sporty driving dynamics and refined efficiency. Emissions compliance was achieved through exhaust gas recirculation (EGR), a diesel particulate filter (DPF), and AdBlue-based selective catalytic reduction (SCR), allowing most units to meet Euro 5 standards, with later builds achieving full Euro 6 compliance.
One documented concern is high-pressure fuel pump (HPFP) wear or failure, particularly under high-load operation or with prolonged use of substandard diesel fuel. This issue, highlighted in Daimler Service Information Bulletin 70.00-P-1010-6, is linked to contamination or lubricity issues in ultra-low-sulfur diesel (ULSD). From 2014, revised pump internals and updated fuel filtration were introduced to improve durability.
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 sequential twin-turbo setup provides strong, lag-free torque delivery ideal for spirited driving but requires strict adherence to 15,000 km oil change intervals to protect the high-pressure fuel pump and turbo actuators. MB 229.51 or 229.5 oil is critical due to its specific formulation for diesel particulate filter compatibility and fuel system protection. Cold-start idling should be limited to reduce EGR soot accumulation. The Bosch CRS 3-18 fuel pump demands ultra-low-sulfur diesel (ULSD) meeting EN 590 standards to prevent premature wear. Post-2014 models feature improved fuel filtration; pre-2014 units benefit from upgraded inline filters. EGR, DPF, and SCR systems require periodic cleaning to maintain emissions compliance and prevent regeneration-related limp mode.
Oil Specs: Requires MB 229.51 (5W-30) or MB 229.5 (5W-40) specification (Daimler Service Manual W204/W212). Ensures DPF regeneration and fuel pump longevity.
Emissions: Euro 5 certification applies to pre-2014 models only (VCA Type Approval #VCA/EMS/9405). Euro 6 compliance applies to 2014–2016 models with AdBlue injection.
Power Ratings: Measured under DIN 70020 standards. Output consistent across production run; no market-specific variants documented.
Daimler Technical Information System (TIS): Docs 651.00-2001, 070.00-3100, SIB 70.00-P-1010-6
VCA Type Approval Database (VCA/EMS/9405)
ISO 1585:1976 Road vehicles — Engine test code — Net power
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.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block, just below the intake manifold (Daimler TIS 651.940-0100). The 9th digit of the VIN identifies the engine type ('D' for diesel). Pre-2014 units have a single-stage fuel filter housing; post-2014 models use a dual-stage design with water separator. Critical differentiation from OM 651.910: OM 651.940 has higher power output (150 kW vs 125 kW), increased torque (500 Nm vs 400 Nm), and includes AdBlue SCR system on post-2014 Euro 6 models. Service parts require chassis number verification—cooling manifolds for W212 models differ from W204 due to routing revisions (Daimler SIB 70.00-P-1010-6).
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.
Find answers to most commonly asked questions about MERCEDES-BENZ OM651940.
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