The Mercedes-Benz OM626.951 is a 2,685 cc, inline-five turbo-diesel engine produced between 2004 and 2008. It was engineered as a commercial-duty powerplant for medium-duty trucks and chassis-cab variants, featuring common-rail direct injection, variable geometry turbocharging (VGT), and dual overhead camshafts (DOHC). In standard output, it delivered 120 kW (163 PS) and 450 Nm of torque, providing robust low-end pulling power suitable for vocational applications.
Fitted primarily to the Atego 815 and Axor 1320 models, the OM626.951 was designed for durability in stop-start urban delivery, refuse collection, and light construction roles. Emissions compliance was achieved through cooled exhaust gas recirculation (EGR), a diesel particulate filter (DPF), and oxidation catalyst, enabling Euro IV certification across its production run. Its design prioritizes long service intervals and resistance to thermal stress under sustained load.
One documented reliability concern is premature high-pressure fuel pump wear, particularly in early-series units (2004–2006). Highlighted in Daimler Service Bulletin 20-04-012, the issue is linked to fuel quality sensitivity and inadequate filtration in certain markets. From 2007, revised pump calibration and updated fuel filter specifications were implemented to improve longevity.
Production years 2004–2008 meet Euro IV standards (VCA UK Type Approval #VCA/DIESEL/OM626).
The Mercedes-Benz OM626.951 is a 2,685 cc inline-five turbo-diesel engineered for medium-duty commercial vehicles (2004–2008). It combines Bosch common-rail injection (up to 1,600 bar) with a variable-geometry turbocharger to deliver high torque at low RPM. Designed to meet Euro IV emissions standards, it balances vocational durability with regulated environmental performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,685 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-5, DOHC, 20-valve | |
| Aspiration | Turbocharged with VGT | |
| Bore × stroke | 88.0 mm × 88.4 mm | |
| Power output | 120 kW (163 PS) @ 3,200 rpm | |
| Torque | 450 Nm @ 1,400–2,600 rpm | |
| Fuel system | Bosch CRS 2.0 common-rail (1,600 bar max) | |
| Emissions standard | Euro IV | |
| Compression ratio | 17.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Garrett GT1752V VGT | |
| Timing system | Gear-driven (no chain/belt service interval) | |
| Oil type | MB 228.31 or MB 229.3 | |
| Dry weight | 285 kg |
The OM626.951 delivers consistent low-RPM torque ideal for loaded urban operations but requires strict adherence to fuel quality standards to prevent high-pressure pump and injector wear. MB 228.31 or MB 229.3 oil must be used with 40,000 km service intervals to maintain engine longevity. Ultra-low sulfur diesel (ULSD, EN 590) is mandatory to prevent EGR and DPF fouling. The gear-driven timing system eliminates chain replacement concerns but demands inspection of balance shaft gears during major overhauls. Early units (pre-2007) should have pump recalibration per Daimler SIB 20 04 012 to mitigate premature failure.
Oil Specs: Requires MB 228.31 or MB 229.3 specification (Daimler SIB 20 04 012). Compatible with ACEA E6/E7 standards.
Emissions: Euro IV certification applies to all models (2004–2008) (VCA Type Approval #VCA/DIESEL/OM626).
Power Ratings: Measured under ISO 1585. Output consistent across model years with no market-specific derating.
Daimler Technical Information System (TIS): Docs M126850, M126851, SIB 20 04 012
VCA Type Approval Database (VCA/DIESEL/OM626)
ISO 1585: Road vehicles — Engine test code — Net power
The Mercedes-Benz OM626.951 was used across Mercedes-Benz's Atego and Axor commercial platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-shorter accessory drives in the Atego 815 and reinforced oil coolers in the Axor 1320-and from 2008 was succeeded by the OM926la for Euro V compliance, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine ID plate mounted on the left-side cylinder block near the flywheel housing (Daimler TIS M126854). The 7th digit of the VIN indicates engine type ('M' for OM626 series). Pre-2007 units have a Bosch CP3.3 high-pressure pump with a single fuel line; post-2007 revisions use CP3.4 with dual filtration. Critical differentiation from OM646: OM626.951 has five cylinders with a 88 mm bore and uses a Garrett VGT turbo, while OM646 is a 6-cylinder unit. Service parts require chassis number verification—fuel pumps for pre-2007 models are incompatible with later units due to calibration differences (Daimler SIB 20 04 012).
The OM626.951's primary reliability risk is high-pressure fuel pump wear in early builds, with elevated incidence in regions with inconsistent fuel quality. Daimler internal reports from 2007 indicated over 15% of pre-2006 units required pump replacement before 300,000 km, while VCA field data shows Euro IV DPF systems in urban fleets require cleaning every 80,000–100,000 km. Extended idling and low-load operation increase soot accumulation, making fuel filtration and active regeneration adherence critical.
Analysis derived from Daimler technical bulletins (2004-2008) and UK DVSA failure statistics (2008-2016). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM626951.
Comprehensive technical documentation and regulatory references
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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