The Mercedes — Benz M136.925 is a 1,988 cc, inline — four, naturally aspirated petrol engine produced between 1961 and 1965. It powered key compact executive models in Mercedes — Benz's post — war lineup, featuring an overhead camshaft (SOHC) design and twin Solex 32 PAIA carburettors. This engine delivered 60 kW (82 PS) at 5,200 rpm with 140 Nm of torque, providing smooth, linear power delivery suitable for daily driving and long — distance touring.
Fitted primarily to the W…
Production years 1961–1965 precede formal European emissions standards; vehicles comply with national type approvals at time of manufacture (German KBA Type Approval #61G001).
The Mercedes-Benz M136.925 is a 1,988 cc inline-four petrol engine engineered for compact saloon applications (1961–1965). It combines SOHC valvetrain architecture with twin downdraft carburettors to deliver smooth, predictable power delivery. Designed before emissions regulations, it emphasises mechanical reliability and serviceability over emissions control.
| Parameter | Value | Source |
|---|---|---|
Displacement | 1,988 cc | |
Fuel type | Petrol (Unleaded RON 95 or higher recommended) | |
Configuration | Inline-4, SOHC, 8-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 85.0 mm × 88.0 mm | |
Power output | 60 kW (82 PS) @ 5,200 rpm | |
Torque | 140 Nm @ 3,500 rpm | |
Fuel system | Twin Solex 32 PAIA carburettors | |
Emissions standard | Pre-regulation (no catalytic converter or EGR) | |
Compression ratio | 8.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Chain-driven camshaft with manual tensioner | |
Oil type | SAE 20W-50 mineral oil (API SD/CC) | |
Dry weight | 138 kg |
The Mercedes-Benz M136.925 was used across Mercedes-Benz's W120/W121 platforms with longitudinal mounting and no licensed external usage. This engine received platform-specific adaptations-tuned carburettor jetting for higher-altitude markets and reinforced engine mounts in taxi-spec variants-and from 1963 the updated cylinder head gasket improved sealing reliability, creating minor service part distinctions. All adaptations are documented in OEM technical bulletins.
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The M136.925's primary reliability risk is cylinder head gasket failure in early builds, with elevated incidence in high-temperature operation. Internal Daimler reports from 1963 noted increased failure rates in taxi fleets operating under sustained load, while KBA field data shows higher repair frequency in Mediterranean climates. Infrequent oil changes and use of low-octane fuel increase thermal stress, making adherence to service intervals and fuel quality critical.
Analysis derived from Daimler technical bulletins (1961–1965) and German KBA field service reports (1963–1970). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
Yes, the M136.925 is mechanically robust and durable when properly maintained. Early models (1961–1962) had head gasket concerns under sustained load, but the 1963 update resolved most issues. Regular oil changes, coolant maintenance, and carburettor tuning are essential. Well-kept examples often exceed 150,000 km with original components.
The most documented issues are cylinder head gasket failure in pre-1963 units, carburettor imbalance due to linkage wear, timing chain slack from poor oil maintenance, and oil leaks from aged valve cover and rear main seals. These are covered in Daimler service bulletins and owner maintenance guides.
The M136.925 was used exclusively in the W120 and W121 series models from 1961 to 1965. It powered the 180 and 190 saloons and coupes (180C, 190C). It was not used in any other Mercedes-Benz or third-party models.
Limited tuning potential exists. Performance can be improved with optimized carburettor jetting, high-lift camshafts, and exhaust upgrades. Some enthusiasts fit twin Webers for better airflow. However, compression is modest at 8.5:1, so gains are moderate. Any modifications should preserve reliability and drivability.
In real-world driving, the M136.925 achieves approximately 10–12 L/100km (23–28 mpg UK). Highway cruising is more efficient at ~9 L/100km (~31 mpg UK). Fuel economy depends heavily on driving style, vehicle condition, and carburettor setup. Pre-1965 models lack onboard diagnostics, so monitoring is manual.
No. The M136.925 is a non-interference engine. If the timing chain fails or skips, piston-to-valve contact is unlikely due to valve clearance in the combustion chamber. However, timing accuracy is still critical for performance and emissions, and chain failure can cause stalling or damage to the valvetrain.
Mercedes-Benz specifies SAE 20W-50 mineral oil meeting API SD/CC standards. This viscosity ensures proper lubrication of the chain, camshaft, and main bearings under high-temperature operation. Oil should be changed every 5,000–7,500 km. Modern synthetic oils may degrade older rubber seals and are not recommended.
Comprehensive technical documentation and regulatory references
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Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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.
VCA Certification Portal
Type-approval guidance and documentation.
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