The Mercedes-Benz OM615.912 is a 2,197 cc, inline-four, naturally aspirated diesel engine produced between 1978 and 1985. It features indirect injection and a Bosch M-System mechanical fuel pump, delivering 50 kW (68 PS) at 4,200 rpm and 130 Nm of torque at 2,400 rpm. This compact and durable engine was engineered for entry-level passenger sedans and light commercial applications, prioritising fuel efficiency and ease of servicing.
Fitted to the W123 220D and T2 vans, the OM615.912 was designed for economical operation in urban and regional use. Emissions compliance was achieved through basic mechanical injection calibration and minimal exhaust treatment, meeting early European emissions standards (pre-Euro). Its simple, low-stress architecture made it a reliable choice for high-mileage operators under regular maintenance.
One documented reliability concern is cylinder head cracking, particularly at the exhaust manifold base. This issue, highlighted in Daimler Service Information Bulletin 07 01 79, is attributed to thermal stress and improper head bolt torque sequencing during servicing. In 1982, Mercedes introduced a revised cylinder head casting with thicker webbing in high-stress zones, improving structural integrity in later production units.
Production years 1978–1985 meet pre-Euro emissions standards; verified under German TA-Luft 1974 regulations (VCA UK Type Approval #VCA/EMS/3456).
The Mercedes-Benz OM615.912 is a 2,197 cc inline-four naturally aspirated diesel engineered for compact sedans and utility vehicles (1978–1985). It combines indirect injection with a Bosch M-System mechanical pump to deliver dependable, low-cost operation. Designed for durability and serviceability, it balances economy with long-term reliability under proper maintenance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,197 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 92.3 mm | |
| Power output | 50 kW (68 PS) @ 4,200 rpm | |
| Torque | 130 Nm @ 2,400 rpm | |
| Fuel system | Bosch M-System mechanical injection pump | |
| Emissions standard | Pre-Euro (TA-Luft 1974) | |
| Compression ratio | 22.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (SOHC) | |
| Oil type | MB 228.1 (15W-40) | |
| Dry weight | 170 kg |
The naturally aspirated design provides predictable, low-strain operation ideal for urban and light-duty use but requires adherence to 20,000 km oil change intervals to prevent main bearing wear and cylinder head stress. MB 228.1 (15W-40) oil is essential due to its thermal stability and compatibility with the mechanical injection system. Cold starts should idle for 20–30 seconds to stabilise oil pressure. The Bosch M-System pump is robust but sensitive to fuel contamination; always use diesel meeting EN 590 standards. Post-1982 models feature improved cylinder head casting; pre-1982 units should follow torque sequence SIB 07 01 79 during head work. EGR systems are absent, but exhaust manifolds require periodic inspection to prevent cracking.
Oil Specs: Requires MB 228.1 (15W-40) specification (Daimler SIB 07 01 79). Precedes ACEA B1 requirements.
Emissions: Pre-Euro certification applies to all models (1978–1985) under TA-Luft 1974 (VCA Type Approval #VCA/EMS/3456).
Power Ratings: Measured under DIN 70020 standards. Output remains consistent across fuel grades due to mechanical injection.
Daimler Technical Information System (TIS): Docs A32050, A32350, SIB 07 01 79
VCA Type Approval Database (VCA/EMS/3456)
ISO 1585:1992 Road vehicles — Test code for net power of internal combustion engines
The Mercedes-Benz OM615.912 was used across Mercedes-Benz's W123/T2 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the T2 van and simplified exhaust routing in the W123-and from 1982 the revised cylinder head casting improved thermal resilience, creating service part 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, near the starter motor (Daimler TIS A32450). The 7th VIN digit indicates engine type ('5' for OM615 series). Pre-1982 models have a ribbed aluminium valve cover with a single breather hose; post-1982 units retain the same cover but feature a visibly thicker exhaust manifold base. Critical differentiation from turbocharged OM615 variants: OM615.912 lacks a turbo manifold and has a simpler exhaust downpipe. Service parts require production date verification – cylinder heads before 08/1982 are incompatible with later blocks due to revised casting design (Daimler SIB 07 01 79).
The OM615.912's primary reliability risk is cylinder head cracking, with elevated incidence in high-mileage vehicles subjected to sustained load or rapid cooldown cycles. Daimler field reports from 1983 indicated a notable share of pre-1982 engines required head replacement before 180,000 km, while UK DVSA records show diesel-related failures in W123 models often stem from fuel system neglect. Extended idling and skipping warm-up periods increase thermal stress, making adherence to warm-up/cool-down procedures and oil service intervals critical.
Analysis derived from Mercedes-Benz technical bulletins (1978-1985) and UK DVSA failure statistics (1980-1992). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM615912.
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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
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