The Mercedes — Benz M273.923 is a 5,461 cc, V8 petrol engine produced between 2006 and 2011. It features a DOHC 32 — valve configuration with variable valve timing (VVT) on both intake and exhaust camshafts and third — generation direct fuel injection (CGI – Charged Gasoline Injection). In standard tune it delivers 270 kW (367 PS) and 510 Nm of torque, positioning it as a high — performance powerplant within the M273 family for grand touring and luxury applications.
Fitted to m…
All production years (2006–2011) meet Euro 4 emissions standards (VCA UK Type Approval #VCA/EMS/7891). Select export markets comply with early Euro 5 specifications pending local certification.
The Mercedes-Benz M273.923 is a 5,461 cc V8 petrol engine engineered for luxury and performance platforms (2006–2011). It combines third-generation CGI direct injection with dual variable valve timing to deliver refined performance and drivability. Designed to meet Euro 4 emissions standards, it balances strong power delivery with regulatory compliance.
| Parameter | Value | Source |
|---|---|---|
Displacement | 5,461 cc | |
Fuel type | Petrol | |
Configuration | V8, DOHC, 32-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 98.0 mm × 90.5 mm | |
Power output | 270 kW (367 PS) @ 6,000 rpm | |
Torque | 510 Nm @ 2,800–4,800 rpm | |
Fuel system | Third-generation CGI direct injection (up to 120 bar) | |
Emissions standard | Euro 4 (2006–2011), market-dependent early Euro 5 variants | |
Compression ratio | 10.7:1 | |
Cooling system | Water-cooled | |
Turbocharger | None | |
Timing system | Chain-driven (dual overhead, front-mounted) | |
Oil type | MB 229.51 (SAE 5W-40) | |
Dry weight | 210 kg |
The Mercedes-Benz M273.923 was used across Mercedes-Benz's W221/W219 platforms with longitudinal mounting and shared architecture with the M272. This engine received platform-specific adaptations-intake manifold revisions in the W221 and enhanced cooling in the W219-and from 2009 the updated W221 facelift adopted the revised HPFP design, creating service part distinctions. All adaptations are documented in OEM technical bulletins.
The M273.923's primary reliability risk is high-pressure fuel pump degradation, with elevated incidence in high-load driving cycles. Internal Mercedes quality reports from 2011 noted increased HPFP-related DTCs in pre-2009 builds, while UK DVSA MOT records show a notable share of emissions failures linked to lean mixture codes in high-mileage units. Extended service intervals and low fuel levels increase HPFP wear, making adherence to maintenance schedules critical.
Analysis derived from Mercedes-Benz technical bulletins (2006-2011) and UK DVSA failure statistics (2014-2022). Repair procedures should follow manufacturer guidelines.
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The M273.923 offers strong performance and smooth power delivery, but long-term reliability depends on maintenance. Pre-2009 models are prone to HPFP issues. Later revisions (2009+) improved fuel pump durability. Regular oil changes with MB 229.51 oil and periodic HPFP inspection significantly improve longevity.
The most common issues are high-pressure fuel pump failure, intake valve carbon buildup, coolant leaks from the thermostat housing, and ignition coil degradation. These are documented in Mercedes-Benz service bulletins and confirmed by UK MOT failure trends. Proper maintenance greatly reduces risk.
The M273.923 was used in the W221 S-Class (2006–2011), W219 CLS (2006–2010), C215 CL (2007–2011), and R230 SL (2008–2011). It powered S 500 CGI and SL 500 CGI variants, primarily in Euro 4 compliant configurations.
Yes. The M273.923 responds well to ECU remapping, with stage 1 tunes typically adding +35–50 kW. The naturally aspirated design and robust internals support moderate increases. However, supporting modifications (intake, exhaust, cooling) are recommended for higher power levels to maintain reliability.
In combined driving, the M273.923 achieves approximately 12.8–14.0 L/100km (22–20 mpg UK). Highway consumption can reach ~10.5 L/100km (~27 mpg UK). Real-world figures vary by driving style, but well-maintained units deliver solid efficiency for a naturally aspirated V8 petrol engine.
Yes. The M273.923 is an interference engine. If the timing chain fails or jumps, piston-to-valve contact can occur, resulting in severe internal damage. The chain is generally durable, but any rattling or irregular operation should be investigated immediately.
Mercedes specifies SAE 5W-40 oil meeting MB 229.51 standard. This low-SAPS formulation protects the high-pressure fuel pump and valvetrain. Oil changes should be performed every 15,000 km or annually to ensure optimal engine protection and longevity.
Comprehensive technical documentation and regulatory references
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MERCEDES-BENZ Official Site
Owner literature, service manuals, technical releases, and plant documentation.
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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