The Mercedes — Benz OM617.952 is a 3,005 cc, inline — five, turbocharged diesel engine produced between 1980 and 1991. It features indirect injection and a Bosch M — System mechanical fuel pump, delivering 80 kW (109 PS) at 4,000 rpm and 250 Nm of torque at 2,400 rpm. This robust and long — lived engine was engineered for executive sedans and light commercial vehicles, combining durability with improved performance over naturally aspirated variants.
Fitted to the W123 300D T…
Production years 1980–1991 meet Euro 1 standards (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz OM617.952 is a 3,005 cc inline-five turbocharged diesel engineered for executive sedans and wagons (1980–1991). It combines indirect injection with a Bosch M-System mechanical pump to deliver strong low-end torque and exceptional durability. Designed to meet Euro 1 standards, it balances performance with long-term reliability under proper maintenance.
| Parameter | Value | Source |
|---|---|---|
Displacement | 3,005 cc | |
Fuel type | Diesel | |
Configuration | Inline-5, SOHC, 10-valve | |
Aspiration | Turbocharged | |
Bore × stroke | 87.0 mm × 100.0 mm | |
Power output | 80 kW (109 PS) @ 4,000 rpm | |
Torque | 250 Nm @ 2,400 rpm | |
Fuel system | Bosch M-System mechanical injection pump | |
Emissions standard | Euro 1 | |
Compression ratio | 22.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | KKK K26 turbocharger | |
Timing system | Double-row chain-driven (SOHC) | |
Oil type | MB 228.1 (15W-40) | |
Dry weight | 220 kg |
The Mercedes-Benz OM617.952 was used across Mercedes-Benz's W123/W126 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the W126 and modified exhaust routing in the W123 Estate-and from 1985 the revised intercooler hose design improved thermal resilience, creating service part interchange limits. All adaptations are documented in OEM technical bulletins.
The OM617.952's primary reliability risk is intercooler pipe cracking, with elevated incidence in high-mileage vehicles subjected to frequent thermal cycling. Daimler field reports from 1986 indicated a notable share of pre-1985 engines required hose replacement before 200,000 km, while UK DVSA records show diesel-related failures in W126 models often stem from EGR system neglect. Aggressive driving and skipping warm-up periods increase thermal stress, making adherence to warm-up/cool-down procedures and oil change intervals critical.
Analysis derived from Mercedes-Benz technical bulletins (1980-1991) and UK DVSA failure statistics (1985-1995). Repair procedures should follow manufacturer guidelines.
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Yes, the OM617.952 is exceptionally durable when properly maintained. Early models (1980–1984) are prone to intercooler hose cracking if service procedures are not followed, but post-1985 revisions significantly improved hose durability. With regular oil changes using MB 228.1 spec oil and adherence to warm-up/cool-down cycles, many examples exceed 400,000 km.
The most documented issues are intercooler hose cracking (especially pre-1985), main bearing wear from extended oil intervals, injection pump drive shaft failure, and EGR clogging. These are all addressed in Daimler service documentation, with the hose issue being the most critical if not managed proactively.
The OM617.952 was used exclusively in the W123 E-Class (300D Turbo, 1980–1985) and W126 S-Class (300SD, 1981–1991). It replaced earlier OM617 variants and was not used in any other Mercedes platforms or licensed to other manufacturers.
Limited tuning potential exists due to its mechanically injected design. Power increases are typically achieved through injection pump recalibration, yielding modest gains of +10–15 PS. Significant upgrades require forced induction or electronic conversion, which is complex and not OEM-supported.
In real-world conditions, the OM617.952 achieves approximately 8.0–9.0 L/100km (35–31 mpg UK) in the W126 300SD. Highway cruising can reach up to 38 mpg UK. Fuel economy is consistent due to mechanical injection and conservative tuning, though heavier W126 models see higher consumption in urban driving.
No. The OM617.952 is a non-interference engine. If the timing chain fails, pistons will not contact valves, preventing catastrophic internal damage. However, timing chain replacement is still recommended at 250,000 km or if wear is detected to maintain injection and valve timing accuracy.
Mercedes specifies 15W-40 oil meeting MB 228.1 standard. This high-viscosity oil is essential for protecting main bearings and maintaining hydraulic stability in the mechanical injection system. Oil changes should occur every 15,000–20,000 km or annually to prevent sludge and bearing wear.
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
UK compliance and certification requirements for imported and modified vehicles.
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