The Mercedes — Benz M 273.961 is a 5,461 cc, 90° V8 petrol engine produced between 2005 and 2011. It features dual overhead camshafts (DOHC), variable valve timing (VVT) on intake and exhaust camshafts, and sequential multi — port fuel injection. In standard tune, it delivered 225 kW (306 PS) in the E — Class, with higher outputs reaching 285 kW (388 PS) in S — Class and CL — Class applications, producing torque between 460–530 Nm.
Fitted to key luxury platforms including the W21…
All production years 2005–2011 meet Euro 4 emissions standards (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz M 273.961 is a 5,461 cc V8 petrol engine engineered for luxury sedan and coupe applications (2005–2011). It combines dual overhead camshafts with variable valve timing on both intake and exhaust to deliver smooth power delivery and strong mid-range torque. Designed to meet Euro 4 standards, it balances performance with drivability in high-end models.
| Parameter | Value | Source |
|---|---|---|
Displacement | 5,461 cc | |
Fuel type | Petrol | |
Configuration | 90° V8, DOHC, 32-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 96.9 mm × 92.4 mm | |
Power output | 225–285 kW (306–388 PS) | |
Torque | 460–530 Nm @ 2,700–4,000 rpm | |
Fuel system | Sequential multi-port fuel injection | |
Emissions standard | Euro 4 | |
Compression ratio | 10.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | N/A | |
Timing system | Dual chain (primary and secondary), non-interference design | |
Oil type | MB 229.5 (SAE 5W-40) | |
Dry weight | 210 kg |
The Mercedes-Benz M 273.961 was used across Mercedes-Benz's W211/W221/R230 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-intake tuning for the SL-Class and revised engine mounts for the S-Class-and from 2008, updated camshaft adjusters were introduced to improve longevity, creating minor service part differences. All adaptations are documented in OEM technical bulletins.
The M 273.961's primary reliability risk is camshaft adjuster wear in pre-2008 builds, with elevated incidence in vehicles with extended oil intervals. Internal Mercedes-Benz quality reports from 2009 indicated a significant number of pre-facelift engines required adjuster replacement before 120,000 km, while UK DVSA MOT data links a portion of engine-related failures to oil system neglect. Cold-start cycles and infrequent oil changes increase adjuster wear, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2007-2012) and UK DVSA failure statistics (2010-2020). Repair procedures should follow manufacturer guidelines.
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The M 273.961 is generally robust when maintained properly. Pre-2008 models are prone to camshaft adjuster wear, which can lead to timing issues if ignored. Later models (post-2008) benefited from updated phasers and improved durability. Regular oil changes with MB 229.5 spec oil every 15,000 km are essential. With proper care, these engines can exceed 250,000 km.
The most documented issues are camshaft adjuster wear (especially pre-2008), intake carbon buildup affecting idle, oil leaks from valve covers and rear main seal, and coolant leaks from the plastic thermostat housing. These are confirmed in Mercedes-Benz service bulletins and field reports. Preventative maintenance greatly reduces risk.
The M 273.961 was used in several flagship models: W211 E-Class (E 350/E 500), W221 S-Class (S 350/S 500/S 550), R230 SL-Class (SL 350/SL 500/SL 550), C219 CLS-Class, and C215 CL-Class. All applications are Euro 4 compliant and feature longitudinal mounting. No external licensing to other manufacturers occurred.
Yes, though less common than turbo engines. ECU remapping can yield +20–30 kW gains safely by optimizing ignition and fuel maps. Aftermarket headers, intake, and exhaust can further enhance flow. However, the naturally aspirated design limits high-end gains. Tuning should preserve factory safety margins and cooling capacity.
In combined driving, expect 11–14 L/100km (20–26 mpg UK). Highway cruising can achieve ~9.5 L/100km (30 mpg UK), while city driving may exceed 16 L/100km (18 mpg UK). Larger vehicles like the S-Class consume more. Real-world figures depend heavily on driving style and vehicle weight.
No. The M 273.961 uses a non-interference valvetrain design. If the timing chain fails, pistons will not contact valves, preventing catastrophic internal damage. However, timing integrity is still critical for performance and emissions compliance.
Mercedes-Benz specifies SAE 5W-40 oil meeting MB 229.5 standard. This low-ash formulation protects the valve train and is compatible with oxygen sensors and catalytic converters. Oil changes every 15,000 km or annually are recommended to maintain adjuster and lifter longevity.
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
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VCA Certification Portal
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