The Mercedes — Benz M103.982 is a 2,962 cc, inline — six, naturally aspirated petrol engine produced between 1992 and 1993. It features a dual overhead camshaft (DOHC) design with 24 valves and electronic fuel injection (Bosch LH — Jetronic), delivering smooth high — RPM performance and refined operation. This engine was engineered for durability and linear power delivery, making it suitable for executive sedans and coupes.
Fitted to models such as the W124 300E and W126 3…
Production years 1992–1993 meet Euro 1 standards .
The Mercedes-Benz M103.982 is a 2,962 cc inline-six naturally aspirated engine engineered for executive sedans and coupes (1992–1993). It combines DOHC 24-valve architecture with Bosch LH-Jetronic fuel injection to deliver refined high-RPM performance and smooth power delivery. Designed to meet Euro 1 emissions standards, it balances driving comfort with mechanical robustness.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,962 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 87.0 mm × 83.0 mm | |
Power output | 138 kW (188 PS) @ 5,700 rpm | |
Torque | 265 Nm @ 3,700 rpm | |
Fuel system | Bosch LH-Jetronic electronic fuel injection | |
Emissions standard | Euro 1 | |
Compression ratio | 10.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Double-row roller chain (single-stage) | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 185 kg |
The Mercedes-Benz M103.982 was used across Mercedes-Benz's W124/W126 platforms with longitudinal mounting. This engine received platform-specific adaptations-longer intake manifold in the W124 and revised exhaust routing in the W126-and incorporates post-1991 camshaft hardening upgrades, creating interchange limits. All adaptations are documented in OEM technical bulletins.
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Field reports and technical service bulletins highlight component wear patterns under high-load operation. Adherence to manufacturer service intervals and approved fluid specifications is critical for long-term reliability.
Analysis derived from manufacturer technical service bulletins and industry workshop records. Repair procedures should follow manufacturer guidelines.
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The M103.982 offers smooth performance and solid build quality, incorporating post-1991 camshaft hardening improvements that significantly reduce the risk of lobe wear. When maintained with MB 229.1 10W-40 oil and timely servicing, it demonstrates strong long-term reliability in well-cared-for examples.
Key issues include residual camshaft lobe wear in high-mileage units, coolant leaks from the thermostat housing, idle instability from LH-Jetronic system faults, and valve cover oil leaks. These are documented in Mercedes-Benz service bulletins and verified through technical diagnostics. Preventative maintenance greatly reduces occurrence.
The M103.982 was installed in the W124 300E (1992–1993) and W126 300SE (1992–1993). All are Euro 1-compliant petrol models. This 24-valve variant is distinct from the 12-valve M103.940 used in other trims and benefits from post-1991 durability upgrades.
Limited tuning potential exists. ECU remapping is not applicable due to analog LH-Jetronic system. Performance gains are typically achieved through induction, exhaust, and ignition upgrades. Stock internals are robust, but significant power increases require internal modifications. Realistic gains are +15–25 PS with bolt-ons.
Moderate for its era. In a W124 300E, combined consumption is ~9.8 L/100km (29 mpg UK). Highway driving yields ~7.8 L/100km (36 mpg UK), while city use can exceed 12.0 L/100km (24 mpg UK). Fuel quality (EN 228) and engine condition significantly affect real-world figures.
Yes. The M103 series is an interference engine. If the timing chain fails or jumps, piston-to-valve contact is likely, resulting in severe internal damage. While chain life is generally long, any signs of wear or noise should prompt immediate inspection to prevent catastrophic failure.
Mercedes-Benz specifies SAE 10W-40 oil meeting MB 229.1 standard. Use of this exact specification is critical to protect camshafts and maintain oil pressure. Change intervals should not exceed 15,000 km or one year, whichever comes first, to ensure optimal lubrication and longevity.
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DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
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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.
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