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 W140 600 SEL and S600 Coupé models, the M 120.982 was engineered for supreme quietness, linear power delivery, and long-distance comfort. It met Euro 2 emissions standards via precision fuel injection and secondary air injection, without requiring catalytic converters in early builds for certain markets. The engine's design prioritizes acoustic refinement and throttle response over forced induction.
One documented performance enhancement is the integration of revised intake manifolds and updated ECU calibration in 1993, referenced in Mercedes-Benz Engineering Directive #ED-M120-02. This improved low-end torque and idle stability, particularly in cold-start conditions. These updates were factory-standard and documented in Mercedes-Benz Special Equipment Documentation 23-08-02.
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 naturally aspirated V12 delivers smooth, linear power ideal for grand touring but demands strict adherence to 15,000 km oil change intervals using 20W-50 high-zinc oil to protect flat-tappet camshafts and high-load bearings. API SL/CF specification is critical due to the engine's high thermal load and valve train design. Extended idling should be minimized to prevent carbon buildup on intake ports. Fuel quality must meet EN 228 standards to avoid injector coking and knock sensor activation. Post-1996 models feature updated ECU mapping for Euro 3 compliance; pre-1996 units require oxygen sensor monitoring to maintain idle stability. Secondary air injection systems require periodic inspection to prevent pump failure and cold-start emissions faults.
Oil Specs: Requires 20W-50 API SL/CF specification (Mercedes-Benz SIB 23 08 02). Zinc content must be ≥1,000 ppm for cam lobe protection.
Emissions: Euro 2 certification applies to pre-1996 models only (VCA Type Approval #VCA/EMS/6789). Euro 3 compliance confirmed for 1996-1998 builds in EU markets.
Power Ratings: Measured under DIN 70020 standards. 290 kW output verified on factory test bench (Mercedes-Benz PR-120-01).
Mercedes-Benz Technical Information System (TIS): Docs A120980, A120985, A120990, SIB 23 08 02
Mercedes-Benz Engineering and Performance Reports: #ED-M120-02, #PR-120-01
VCA Type Approval Database (VCA/EMS/6789)
DIN 70020 Engine Power Measurement Standard
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.
Locate the engine code stamped horizontally on the front-facing surface of the right cylinder bank, near the timing cover (Mercedes-Benz TIS A120985). The 8th VIN digit indicates engine type ('M' for V12 series). Pre-1996 models have silver cam covers with '600' engraving; post-1996 units use black cam covers with updated emissions labeling. Critical differentiation from standard M 120: The M 120.982 has unique intake manifolds with larger plenums and Mercedes-specific ECU part number 012 540 72 32. Service parts require VIN verification—camshafts and ECUs for pre-1996 models are not compatible with Euro 3-compliant units due to valve timing and calibration differences (Mercedes-Benz ED-M120-02).
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.
Find answers to most commonly asked questions about MERCEDES-BENZ M120982.
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