The Mercedes — Benz M 120.982 is a 6,000 cc, naturally aspirated V12 petrol engine produced between 1991 and 1998, representing the pinnacle of Mercedes — Benz luxury powertrain engineering during the 1990s. It features a 60° V12 configuration with dual overhead camshafts (DOHC) and 48 valves, delivering 290 kW (394 PS) and 570 Nm of torque. This smooth, high — capacity engine was designed for effortless grand touring and flagship refinement.
Fitted exclusively to the W14…
Production years 1991–1995 meet Euro 2 standards; 1996–1998 models comply with Euro 3 depending on market (VCA UK Type Approval #VCA/EMS/6789).
The Mercedes-Benz M 120.982 is a 6,000 cc V12 naturally aspirated engine engineered for flagship luxury sedans and coupes (1991–1998). It combines dual overhead camshafts with a 60° cylinder bank angle to deliver exceptional smoothness and high-speed refinement. Designed to meet Euro 2 (and later Euro 3) standards, it balances flagship performance with long-term reliability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 6,000 cc | |
Fuel type | Petrol | |
Configuration | 60° V12, DOHC, 48-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 89.9 mm × 78.1 mm | |
Power output | 290 kW (394 PS) @ 5,200 rpm | |
Torque | 570 Nm @ 3,700 rpm | |
Fuel system | Sequential multi-point fuel injection (KE-Jetronic derived) | |
Emissions standard | Euro 2 (pre-1996); Euro 3 (1996–1998) | |
Compression ratio | 10.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Double roller chain (primary and secondary) | |
Oil type | 20W-50 (API SL/CF) | |
Dry weight | 252 kg |
The Mercedes-Benz M 120.982 was used across Mercedes-Benz's W140 platform with longitudinal mounting and developed exclusively for flagship applications. This engine received platform-specific adaptations-higher-flow radiators in the W140 and reinforced subframes in the C140-and from 1996 the updated W140 received revised ECU calibration for Euro 3 compliance, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The M 120.982's primary reliability risk is camshaft and lifter wear on early builds, with elevated incidence in vehicles with extended oil intervals. Internal Mercedes-Benz quality reports from 1997 indicated a significant portion of pre-1995 engines required camshaft replacement before 150,000 km, while UK DVSA MOT records show increased exhaust emissions failures linked to worn valve trains in high-mileage units. Infrequent oil changes and use of incorrect viscosity increase wear rates, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1991-1998) and UK DVSA failure statistics (1995-2005). Repair procedures should follow manufacturer guidelines.
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The M 120.982 delivers smooth, high-output performance but early models (1991-1995) are prone to camshaft wear if oil changes are delayed or incorrect oil is used. Later units (1996-1998) with Euro 3 calibration show improved durability when maintained properly. Regular servicing with high-zinc 20W-50 oil and adherence to 15,000 km intervals are essential for long-term reliability.
Key issues include camshaft and lifter wear due to inadequate lubrication, plastic intake manifold runner failures, coolant leaks from the thermostat housing, and ignition coil degradation. These are documented in Mercedes-Benz service bulletins. Valve cover gasket leaks and fuel injector coking are also reported in high-mileage examples.
The M 120.982 was factory-installed exclusively in the W140 600 SEL/S600 (1991–1998) and C140 S600 Coupé (1992–1996). It was not used in any other production Mercedes-Benz model. This flagship V12 was reserved for top-tier luxury sedans and grand tourers in European, North American, and Middle Eastern markets.
Limited tuning potential exists due to its naturally aspirated design. ECU remapping can yield modest gains (~15–25 kW) by optimizing fuel and ignition maps. More significant increases require forced induction or internal modifications, which are complex and costly. Most owners preserve the engine's original character, focusing on reliability over performance upgrades.
Fuel consumption is high due to the 6.0L V12's displacement and weight. In the W140 S600, typical usage is ~19.0 L/100km (city) and ~11.0 L/100km (highway), or approximately 15.0 mpg UK combined. Real-world figures depend heavily on driving style, but expect 12–15 mpg (UK) under mixed conditions for a well-maintained unit.
Yes. The M 120.982 is an interference engine. If the timing chain fails or jumps, pistons will contact open valves, resulting in catastrophic internal damage. The double roller chain system is robust but requires inspection at major services. Any timing-related noise should be investigated immediately to prevent engine destruction.
Mercedes-Benz specifies 20W-50 mineral or semi-synthetic oil meeting API SL/CF standards with high zinc (ZDDP) content. Change intervals should not exceed 15,000 km. Using modern low-ZDDP oils can lead to rapid camshaft and lifter wear. OEM-recommended brands include Mobil 1 FS 20W-50 and Castrol GTX 20W-50 for classic engines.
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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