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 W120 and W121 series models—including the 180 and 190 variants—the M136.925 was engineered for durability, refinement, and mechanical simplicity. Its design prioritised ease of maintenance and long service intervals, aligning with Mercedes-Benz's engineering ethos of the era. As a pre-emissions-regulation engine, it operated without EGR, catalytic converters, or electronic controls, relying on mechanical fuel delivery and ignition systems.
One documented service update involves the cylinder head gasket material, referenced in Daimler Service Information Bulletin 080/1963. Early units experienced occasional head sealing issues under sustained high load, attributed to thermal expansion mismatches between cast iron block and aluminium head. In 1963, an improved composite gasket with enhanced heat resistance was introduced across production, improving long-term sealing integrity.
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 M136.925 delivers smooth, predictable power ideal for classic touring but requires regular carburettor synchronization and ignition tuning to maintain performance. SAE 20W-50 mineral oil is essential for bearing and chain lubrication under high-temperature operation. Cold starts benefit from manual choke operation, and fuel quality (minimum RON 95) prevents pre-ignition in warm climates. The chain-driven camshaft demands periodic tensioner inspection to prevent timing drift. Twin carburettors require careful balancing during maintenance to avoid misfires or rough idle. Owners should use non-ethanol fuel or fuel stabilizers to protect rubber seals and carburettor components during long-term storage.
Oil Specs: Requires SAE 20W-50 mineral oil meeting API SD/CC (Daimler SIB 080/1963). Modern synthetic oils not recommended due to seal compatibility.
Emissions: Pre-regulation design; no formal Euro compliance (KBA Type Approval #61G001). Not equipped with catalytic converter or EGR.
Power Ratings: Measured under DIN 70020 standards. Output consistent across production run; no market-specific variants.
Daimler Technical Information System (TIS): Docs A136-801, A136-802, A136-803, SIB 080/1963
KBA Type Approval Database (61G001)
DIN 70020 Engine Power Measurement Standard
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.
Locate the engine code stamped horizontally on the front face of the cylinder block, just below the intake manifold (Daimler TIS A136-805). The 7th digit of the VIN identifies the engine type ('8' for 180 series with M136.925). Pre-1963 units have a ribbed oil pan and single exhaust outlet; post-1963 models retain same layout. Critical differentiation from M121 engine: M136.925 uses twin Solex carburettors and a longer block; M121 is a smaller 1.9L with a single carburettor. Service parts require model and production date verification—head gaskets before 06/1963 are not interchangeable with later improved versions (Daimler SIB 080/1963).
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.
Find answers to most commonly asked questions about MERCEDES-BENZ M136925.
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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).
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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
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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