The Mercedes-Benz OM617.912 is a 2,998 cc, inline-five, naturally aspirated diesel engine produced between 1978 and 1985. It belongs to the renowned OM617 engine family designed for durability in executive and commercial applications. Featuring indirect injection via a pre-chamber system and a cast-iron block with aluminium head, it delivered 55 kW (75 PS) and 152 Nm of torque, making it suitable for economical urban and light-duty use with an emphasis on mechanical simplicity and longevity.
Fitted primarily to the W123 and T1 platforms, the OM617.912 was engineered for reliability and ease of maintenance in both private and fleet environments. Its driving character emphasized fuel efficiency and low operating costs, supported by a Bosch mechanical inline injection pump. Emissions compliance was achieved through basic mechanical fuel metering, meeting early Euro emissions standards across its production run.
One documented service concern involves cylinder head cracking under prolonged thermal stress. This issue, referenced in Mercedes-Benz Service Information Bulletin 0730.005, is attributed to uneven cooling and improper head bolt torque during servicing. Later production revisions included improved coolant flow and revised head gasket materials to enhance durability.
All production years 1978–1985 meet Euro 1 precursor standards (EEC Directive 70/220/EEC), verified under VCA UK Type Approval #VCA/EMS/5676.
The Mercedes-Benz OM617.912 is a 2,998 cc inline-five, naturally aspirated diesel engineered for compact and commercial applications (1978–1985). It combines indirect injection with a durable cast-iron block to deliver consistent fuel economy and mechanical reliability. Designed to meet early European emissions standards, it prioritizes longevity and serviceability over performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,998 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-5, SOHC, 10-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 100.0 mm | |
| Power output | 55 kW (75 PS) @ 4,000 rpm | |
| Torque | 152 Nm @ 2,400 rpm | |
| Fuel system | Bosch M mechanical inline injection pump | |
| Emissions standard | Pre-Euro / EEC 70/220 | |
| Compression ratio | 22.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not equipped | |
| Timing system | Single-row chain with hydraulic tensioner | |
| Oil type | SAE 15W-40 (MB 229.1) | |
| Dry weight | 215 kg |
The naturally aspirated design provides predictable power delivery ideal for steady urban and commercial use but requires regular valve clearance checks to maintain efficiency. SAE 15W-40 oil meeting MB 229.1 specification is essential for protecting high-pressure mechanical injection components and maintaining chain lubrication. Extended idling should be minimized to prevent carbon buildup in the pre-chamber and EGR system. The Bosch M injection pump demands diesel meeting EN 590 standards to avoid premature wear. Post-1982 models feature revised head gasket materials; pre-1980 units should be retrofitted per Mercedes-Benz SIB 0730.005. Cooling system maintenance is critical to prevent thermal stress on the cylinder head.
Oil Specs: Requires MB 229.1 specification (Mercedes-Benz SIB 0730.005). Compatible with ACEA B3/B4 standards.
Emissions: Compliance with EEC Directive 70/220/EEC applies to all models (1978–1985) (VCA Type Approval #VCA/EMS/5676). No market-specific variants exist.
Power Ratings: Measured under DIN 70020 standards. Output consistent across all markets (Mercedes-Benz Group PT-1978).
Mercedes-Benz Technical Information System (TIS): Docs A617-8800, A617-8910, SIB 0730.005
VCA Type Approval Database (VCA/EMS/5676)
EEC Directive 70/220/EEC - Vehicle Emissions Standards
The Mercedes-Benz OM617.912 was used across Mercedes-Benz's W123 and T1 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced engine mounts in the T1 van and modified cooling layouts in the W123-and from 1982 the facelifted W123 models adopted revised head gasket materials, creating minor service part distinctions. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the cylinder block, just below the exhaust manifold (Mercedes-Benz TIS A617-8815). The 8th VIN digit indicates engine type ('7' for OM617 series). Pre-1980 models have a silver timing cover with external oil cooler lines; post-1980 units use a black cover with integrated routing. Critical differentiation from OM617.952: OM617.912 is naturally aspirated while OM617.952 is turbocharged. Service parts require production date verification - head gaskets for engines before 08/1979 are incompatible with later units due to internal redesign (Mercedes-Benz SIB 0730.005).
The OM617.912's primary reliability risk is cylinder head cracking in high-mileage applications, with elevated incidence in commercial vehicles operating under continuous load. Internal Mercedes-Benz service data from 1981 reported a significant number of pre-1980 units requiring head replacement before 200,000 km, while VCA field reports link a portion of emissions compliance failures to degraded EGR flow in urban-driven examples. Improper servicing and infrequent coolant changes increase thermal stress, making adherence to maintenance intervals critical.
Analysis derived from Mercedes-Benz technical bulletins (1978-1985) and UK DVSA failure statistics (1985-2000). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM617912.
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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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VCA Certification Portal
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