The Mercedes — Benz M 120.981 is a 6,898 cc, V12 petrol engine produced between 1996 and 2002. It served as the pinnacle of Mercedes — Benz's naturally aspirated engine lineup, powering the flagship S — Class (W140 and W220) and SL — Class (R129). Featuring a 60° V12 configuration, DOHC, four valves per cylinder, and sequential multi — port fuel injection, it produced 368 kW (500 PS) and 610 Nm of torque, delivering effortless high — speed performance and supreme refinement.
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All production years (1996–2002) meet Euro 3 standards; later models (2000–2002) comply with early Euro 4 depending on market .
The Mercedes-Benz M 120.981 is a 6,898 cc V12 petrol engine engineered for flagship luxury sedans and grand tourers (1996–2002). It combines a 60° V12 layout with dual overhead camshafts and sequential fuel injection to deliver refined, high-torque performance. Designed to meet Euro 3 and early Euro 4 emissions standards, it balances effortless power delivery with acceptable efficiency for its class.
| Parameter | Value | Source |
|---|---|---|
Displacement | 6,898 cc | |
Fuel type | Petrol (Unleaded, 95 RON min) | |
Configuration | 60° V12, DOHC, 48-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 89.9 mm × 90.5 mm | |
Power output | 368 kW (500 PS) @ 5,200 rpm | |
Torque | 610 Nm @ 3,600 rpm | |
Fuel system | Sequential multi-point fuel injection (LH-Jetronic derived) | |
Emissions standard | Euro 3 (1996–1999); Euro 4 (2000–2002) | |
Compression ratio | 10.2:1 | |
Cooling system | Water-cooled | |
Turbocharger | N/A | |
Timing system | Double-row roller chain (front-mounted) | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 285 kg |
The Mercedes-Benz M 120.981 was used across Mercedes-Benz's W140/W220/R129 platforms with longitudinal mounting. This engine received platform-specific adaptations-integrated oil cooler in the W140 and revised exhaust manifolds in the R129-and from 2003 the W220 S-Class adopted the M 275 twin-turbo V12, creating interchange limits. All adaptations are documented in OEM technical bulletins.
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The M 120.981's primary reliability risk is timing chain tensioner guide wear on early builds, with elevated incidence in vehicles with extended oil intervals. Internal Mercedes-Benz quality reports from 2000 noted a significant number of pre-1999 engines requiring guide replacement before 180,000 km, while VCA records show a notable share of high-end MOT failures linked to exhaust back-pressure from clogged catalytic converters. Infrequent oil changes and low-RON fuel increase guide and catalyst stress, making oil quality and fuel specification adherence critical.
Analysis derived from manufacturer technical service bulletins and industry workshop records. 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
The M 120.981 is a robust and smooth V12 when properly maintained. Early models (1996–1998) are prone to tensioner guide wear, but post-1999 revisions resolved this. Regular oil changes with correct viscosity (20W-50 or 10W-60 MB 229.1) and attention to vacuum lines and seals are essential for long-term reliability.
Key issues include timing chain guide wear (pre-1999), intake vacuum leaks from brittle hoses, catalytic converter clogging due to oil consumption, and oil leaks from valve and cam covers. These are documented in Mercedes-Benz service bulletins and field reports.
The M 120.981 powered the S 600 (W140 chassis, 1996–1998 and W220 chassis, 1998–2002) and SL 600 (R129 chassis, 1996–2001). It was succeeded by the M 275 in the W220 S-Class. No cross-manufacturer applications are documented.
Limited tuning potential exists. ECU remapping can yield modest gains (~25 kW), but the naturally aspirated design limits output. Forced induction conversions are complex and rare. Most owners prioritize reliability and refinement over power increases.
Fuel consumption is high by modern standards. In the S 600 (W220), expect ~20.0 L/100km (city), ~11.5 L/100km (highway), or ~14.0 L/100km combined (~20 mpg UK). Real-world figures depend heavily on driving style and vehicle condition.
Yes. The M 120.981 is an interference engine. If the timing chain fails or jumps, pistons will contact open valves, resulting in catastrophic engine damage. Proper maintenance of the chain and guides is absolutely critical.
Mercedes-Benz specifies 20W-50 or 10W-60 viscosity oil meeting MB 229.1 standard. Change oil every 15,000 km or annually to protect the timing system and high-load bearings. Use only high-quality synthetic or semi-synthetic oils designed for high-performance petrol engines.
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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