The Mercedes Benz OM651.925 is a 2,143 cc, inline-four turbo-diesel engine produced between 2011 and 2016. It features common rail direct injection, variable geometry turbocharging (VGT), and dual overhead camshafts (DOHC), delivering refined performance and strong low-end torque across mid-size and luxury platforms. In standard tune, it produces 150 kW (204 PS) with peak torque of 500 Nm, optimized for responsive driving dynamics and towing capability.
Fitted to models including the W204 C-Class, W212 E-Class, and X204 GLK-Class, the OM651.925 was engineered for enhanced performance while maintaining motorway efficiency. Emissions compliance was achieved via exhaust gas recirculation (EGR), diesel particulate filter (DPF), and selective catalytic reduction (SCR) with AdBlue injection, enabling Euro 6 compliance across most markets from launch, in accordance with EU Regulation (EC) No 715/2007.
One documented reliability concern is high-pressure fuel pump (HPFP) wear, particularly in early-production units, highlighted in Daimler Service Information Bulletin 22 0511. Premature wear is linked to fuel quality and extended service intervals. From 2013, revised pump internals and updated calibration improved longevity, aligning with the transition to full Euro 6 compliance.
Production years 2011–2016 meet Euro 6 emissions standards depending on market (VCA UK Type Approval #VCA/EMS/5679).
The Mercedes Benz OM651.925 is a 2,143 cc inline-four turbo-diesel engineered for mid-size and executive applications (2011–2016). It combines common-rail direct injection with a variable-geometry turbocharger to deliver strong low-end torque and responsive performance. Designed to meet Euro 6 standards, it balances increased output with regulated emissions performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,143 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Turbocharged (VGT) | |
| Bore × stroke | 83.0 mm × 99.0 mm | |
| Power output | 150 kW (204 PS) @ 3,800–4,600 rpm | |
| Torque | 500 Nm @ 1,600–2,400 rpm | |
| Fuel system | Bosch CRS 2.0 common-rail (up to 2,000 bar) | |
| Emissions standard | Euro 6 (2011–2016) | |
| Compression ratio | 15.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Single variable-geometry turbo (Garrett GT1949V) | |
| Timing system | Double-row roller chain (front-mounted) | |
| Oil type | MB 229.51 (SAE 5W-30) | |
| Dry weight | 185 kg |
The OM651.925 delivers high torque ideal for performance driving and towing but requires strict adherence to 15,000 km oil change intervals using MB 229.51–compliant oil to ensure chain and turbo longevity. The Bosch CRS 2.0 fuel system demands ultra-low-sulfur diesel (EN 590) to prevent HPFP wear. SCR-based emissions control requires periodic AdBlue refills and regeneration cycles; neglect can lead to limp mode. Early models (pre-2013) should be inspected for HPFP wear per Daimler SIB 22 0511. EGR and DPF systems benefit from regular highway runs to prevent clogging.
Oil Specs: Requires MB 229.51 specification (Daimler SIB 22 0511). Supersedes ACEA C3 standards for diesel particulate filter protection.
Emissions: Euro 6 certification applies to all OM651.925 units (VCA Type Approval #VCA/EMS/5679), compliant with EU Regulation (EC) No 715/2007.
Power Ratings: Measured under DIN 70020. Output maintained across temperature ranges with ECU adaptive tuning (Daimler TIS Doc. A32175).
Daimler Technical Information System (TIS): Docs A32175, A32176, SIB 22 0511
VCA Type Approval Database (VCA/EMS/5679)
SAE International: J1349 Engine Power Certification Standards
The Mercedes Benz OM651.925 was used across Mercedes Benz's W204/W212/X204 platforms with longitudinal mounting and adapted for transverse applications in front-wheel-drive variants. This engine received platform-specific adaptations-reinforced mounts in the E-Class and revised intake manifolds in the GLK-Class-and from 2013 the facelifted C-Class adopted updated EGR and SCR calibration, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the cylinder block near the timing cover (Daimler TIS A32175). The 8th VIN digit indicates engine type ('6' for OM651 series). All OM651.925 units have black valve covers with blue gaskets, indicating Euro 6 compliance. Critical differentiation from OM651.916: OM651.925 has a larger VGT turbo (Garrett GT1949V) and higher torque output. Service parts require production date verification—HPFP units before 06/2012 are incompatible with later revisions due to internal pump redesign (Daimler SIB 22 0511).
The OM651.925's primary reliability risk is high-pressure fuel pump wear on early builds, with elevated incidence in mixed urban/highway use. Internal Daimler quality reports from 2014 noted a significant number of pre-2013 units requiring HPFP replacement before 160,000 km, while UK DVSA records associate SCR-related faults with AdBlue system neglect in city-driven vehicles. Extended service intervals and poor fuel quality increase pump and injector stress, making fluid quality and schedule adherence critical.
Analysis derived from Daimler technical bulletins (2011–2016) and UK DVSA failure statistics (2014–2022). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM651925.
Comprehensive technical documentation and regulatory references
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
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DVLA: Engine Changes & MoT
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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.
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VCA Certification Portal
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