The Mercedes — Benz OM651.901 is a 2,143 cc, inline — four turbo — diesel engine produced between 2008 and 2016 as part of the company's modular diesel engine family. It features high — pressure common — rail injection (up to 1,800 bar), a variable — geometry turbocharger (VGT), and dual overhead camshafts (DOHC) with four valves per cylinder. In standard tune, it delivers 125 kW (170 PS), with peak torque of 400 Nm, providing responsive mid — range performance ideal for compac…
All production years 2008–2016 meet Euro 5 emissions standards (VCA UK Type Approval #VCA/EMS/7896).
The Mercedes-Benz OM651.901 is a 2,143 cc inline-four turbo-diesel engineered for compact and mid-size sedan and SUV applications (2008–2016). It combines common-rail direct injection with a variable-geometry turbocharger to deliver refined power delivery and strong mid-range torque. Designed to meet Euro 5 standards, it balances performance with emissions control in premium vehicle segments.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,143 cc | |
Fuel type | Diesel | |
Configuration | Inline-4, DOHC, 16-valve | |
Aspiration | Turbocharged | |
Bore × stroke | 83.0 mm × 99.0 mm | |
Power output | 125 kW (170 PS) @ 3,800–4,600 rpm | |
Torque | 400 Nm @ 1,600–2,400 rpm | |
Fuel system | Bosch CRS 2.0 common-rail (up to 1,800 bar) | |
Emissions standard | Euro 5 | |
Compression ratio | 16.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Single variable-geometry turbo (Garrett) | |
Timing system | Chain-driven (double-row primary, secondary chain) | |
Oil type | MB 229.5 (SAE 5W-30) | |
Dry weight | 178 kg |
The Mercedes-Benz OM651.901 was used across Mercedes-Benz's W204/W212/X204 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced mounts in the GLK-Class and revised cooling in the E-Class-and from 2011 the facelifted C-Class models adopted updated SCR calibration, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The OM651.901's primary reliability risk is high-pressure fuel pump failure, with elevated incidence in vehicles exceeding 180,000 km. Daimler internal field reports from 2013 indicated a notable frequency of HPFP breakdowns in pre-2011 units, while UK DVSA data links a significant share of emissions-related MOT failures to DPF saturation in urban-driven compact SUVs. Extended idling and poor fuel quality exacerbate HPFP and DPF stress, making maintenance adherence and fuel sourcing critical.
Analysis derived from Daimler technical bulletins (2008–2016) and UK DVSA failure statistics (2011–2023). Repair procedures should follow manufacturer guidelines.
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The OM651.901 is generally robust with strong build quality, but pre-2011 models are prone to HPFP failure beyond 180,000 km, especially with poor fuel quality. Later revisions (post-2011) improved pump calibration and longevity. When maintained with correct MB 229.5 oil and regular AdBlue top-ups, these engines can reliably exceed 250,000 km in regular service.
Key issues include high-pressure fuel pump failure (especially pre-2011), DPF saturation from short trips, turbo actuator sticking, and timing chain guide wear. These are documented in Daimler service bulletins and field reports. Fuel system failure and regeneration faults are the most frequent causes of major repair.
This 2.1L diesel is used in the C-Class (W204), E-Class (W212), and GLK-Class (X204) models. It powers C 250 CDI, E 250 CDI BlueTEC, and GLK 250 CDI BlueTEC variants produced between 2008 and 2016. All meet Euro 5 standards and use SCR with AdBlue for emissions control.
Yes, the OM651.901 responds well to ECU remapping. Stage 1 tunes typically yield +25–40 kW safely by optimizing boost and injection timing. However, over-tuning can strain the single VGT turbo and fuel system. Supporting modifications like upgraded intercoolers and fuel pressure regulators are recommended for higher stages to maintain reliability in performance applications.
In real-world use, the OM651.901 achieves approximately 6.5–8.0 L/100km (43–35 mpg UK) in the C-Class or E-Class, and 7.5–9.5 L/100km (38–30 mpg UK) in the GLK-Class. Highway driving can yield up to 45 mpg UK. Consumption depends heavily on load, driving style, and DPF regeneration frequency.
Yes. The OM651.901 is an interference engine. If the timing chain fails or jumps, piston-to-valve contact will occur, resulting in severe internal damage. Regular inspection of chain guides and tensioners is essential, especially on high-mileage engines, to prevent catastrophic failure.
Mercedes specifies MB 229.5 (SAE 5W-30) synthetic oil. This formulation is critical for protecting the HPFP, turbocharger, and DPF. Oil must be changed every 15,000 km or annually to prevent sludge buildup and maintain long-term reliability in premium applications.
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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