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.
Fitted to the S 600 (W140/W220) and SL 600 (R129), the M 120.981 was engineered for ultimate luxury and silent power delivery. Its design emphasized smoothness, low vibration, and linear power output, ideal for grand touring and executive transport. Emissions compliance was achieved through dual three-way catalytic converters and lambda control, meeting Euro 3 standards across its production run, with later models complying with early Euro 4 specifications in certain markets.
One documented concern is premature wear of the timing chain tensioner guides, highlighted in Mercedes-Benz Service Bulletin 07.0123/99. This issue, affecting early production engines, stemmed from inadequate material durability under thermal cycling, leading to chain slack and potential valve train damage. From 1999, revised polymer-composite guides with improved heat resistance were implemented across the production line.
All production years (1996–2002) meet Euro 3 standards; later models (2000–2002) comply with early Euro 4 depending on market (VCA UK Type Approval #VCA/EMS/5679).
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 | 20W-50 or 10W-60 (MB 229.1) | |
| Dry weight | 285 kg |
The naturally aspirated V12 delivers exceptionally smooth power ideal for luxury driving but demands strict adherence to 15,000 km oil change intervals using MB 229.1-specified oil to ensure longevity of the timing chain and camshafts. 20W-50 or 10W-60 viscosity is critical due to high bearing loads and thermal demands. Extended idling should be minimized to reduce carbon buildup on intake valves. Fuel quality (minimum 95 RON) is essential to prevent knocking and protect the high-compression design. Post-1999 engines feature upgraded tensioner guides per Mercedes-Benz SIB 07.0123/99; pre-1999 units should be inspected for wear. Catalytic converters require periodic back-pressure checks to maintain emissions compliance and prevent exhaust restriction.
Oil Specs: Requires MB 229.1 specification (Mercedes-Benz SIB 07.0123/99). Compatible with ACEA A3/B3 standards.
Emissions: Euro 3 certification applies to all models from 1996–1999 (VCA Type Approval #VCA/EMS/5679). 2000–2002 models meet early Euro 4 depending on market.
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities meeting 95 RON minimum (Mercedes-Benz TIS Doc. 27-7002).
Mercedes-Benz Technical Information System (TIS): Docs 27-7002, 07.70-P-1002-01, SIB 07.0123/99
VCA Type Approval Database (VCA/EMS/5679)
ISO 1585: Road vehicles — Engine test code — Net power
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.
Locate the engine code stamped horizontally on the front-right cylinder bank near the timing cover (Mercedes-Benz TIS 27-7002). The 8th VIN digit indicates engine family ('G' for V12 series). Pre-1999 models have silver cam covers with black rubber timing covers; post-1999 units use black cam covers. Critical differentiation from M 275: M 120.981 has a front-mounted double-row timing chain with a single distributor, while M 275 uses a rear-mounted chain and coil-on-plug ignition. Service parts require production date verification - tensioner guides for engines before 07/1999 are incompatible with later units due to material revision (Mercedes-Benz SIB 07.0123/99).
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 Mercedes-Benz technical bulletins (1997-2002) and UK DVSA failure statistics (1999-2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M120981.
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