The Mercedes — Benz M273.971 is a 5,461 cc, 90° V8 naturally aspirated petrol engine produced between 2005 and 2011. It features dual overhead camshafts (DOHC), variable valve timing (VVT), and sequential multi — point fuel injection. This engine delivers 225 kW (306 PS) and 460 Nm of torque, engineered for balanced performance and refinement in mid — tier luxury applications. Its architecture includes electronic throttle control and adaptive ignition timing to suppor…
All production years 2005–2011 meet Euro 4 emissions standards .
The Mercedes-Benz M273.971 is a 5,461 cc V8 naturally aspirated petrol engine engineered for mid-tier luxury sedan applications (2005–2011). It combines dual overhead camshafts with variable valve timing to deliver linear power delivery and high-speed refinement. Designed to meet Euro 4 standards, it balances performance with regulatory compliance and long-term drivability.
| 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 kW (306 PS) | |
Torque | 460 Nm @ 2,700–4,250 rpm | |
Fuel system | Sequential multi-point fuel injection (ME 9.7 ECU) | |
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 | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 205 kg |
The Mercedes-Benz M273.971 was used across Mercedes-Benz's W211 and W221 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-variable intake manifolds in the W221 and revised exhaust manifolds in the W211-and from 2008 the updated W211 facelift models adopted revised hydraulic lash adjusters, creating service part interchange limits. All adaptations are documented in OEM technical bulletins.
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Field reports and technical service bulletins highlight component wear patterns under high-load operation. Adherence to manufacturer service intervals and approved fluid specifications is critical for long-term reliability.
Analysis derived from manufacturer technical service bulletins and industry workshop records. Repair procedures should follow manufacturer guidelines.
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The M273.971 is fundamentally robust with strong build quality, but early models (2005–2007) are prone to cam follower wear. Later revisions (post-2008) incorporated improved hydraulic lash adjusters, significantly enhancing durability. When maintained with correct MB 229.5 oil and timely servicing, these engines reliably exceed 150,000 km. Neglecting oil changes or using non-compliant fluids increases risk of valvetrain damage.
Primary issues include camshaft follower wear (especially pre-2008), intake manifold flap linkage failure, valve cover oil leaks, and ignition coil degradation. These are well-documented in Mercedes-Benz service bulletins. Secondary concerns include fuel injector coking and CCV system blockages. Regular inspection and OEM-specified maintenance mitigate most risks effectively.
The M273.971 5.5L V8 was used in several mid-tier luxury models: E350 (W211), S350 (W221), CL350 (C215), and SL350 (R230), produced between 2005 and 2011. It was not licensed to other manufacturers. All applications meet Euro 4 emissions standards, with minor tuning differences across platforms to suit weight and aerodynamics.
Aftermarket ECU tuning is common on the M273971 platform, but increasing boost or altering engine parameters accelerates component wear, impacts emissions compliance, and may void vehicle warranties. Any modifications should be evaluated carefully by a qualified specialist.
Fuel consumption is moderate for a 5.5L V8. In combined driving, expect 11.0–13.0 L/100km (22–26 mpg UK). Highway cruising can achieve ~8.5 L/100km (33 mpg UK), while city driving may exceed 14 L/100km (20 mpg UK). Real-world economy depends heavily on driving style and vehicle weight. No official hybrid or economy modes were offered.
No. The M273.971 uses a non-interference valvetrain design. If the timing chain fails or jumps, the pistons will not contact the valves, preventing catastrophic internal damage. However, timing chain replacement is still recommended at 180,000 km or as condition dictates to maintain synchronization and prevent secondary issues.
Mercedes-Benz specifies SAE 5W-40 oil meeting MB 229.5 standard. This low-ash, high-shear-stability formulation is critical for protecting hydraulic lash adjusters and preventing sludge buildup. Oil changes should occur every 15,000 km or annually. Using non-compliant oils increases risk of cam follower wear and premature engine wear.
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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