The Mercedes — Benz M278.922 is a 5,461 cc, V8 twin — turbocharged petrol engine produced between 2012 and 2017. It features dual overhead camshafts (DOHC), variable valve timing (CAMTRONIC), and direct fuel injection (CGI). In standard output form, it delivers 325 kW (442 PS) and 700 Nm of torque, providing strong performance and smooth power delivery across a broad rev range.
Fitted to models including the W221 S — Class, W213 E — Class, and X166 GLS, the M278.922 was engine…
Production years 2012–2017 meet Euro 6 standards for applicable markets .
The Mercedes-Benz M278.922 is a 5,461 cc V8 twin-turbocharged petrol engine designed for flagship luxury platforms (2012–2017). It combines CGI direct injection with twin-scroll turbochargers to deliver strong mid-range torque and rapid throttle response. Designed to meet Euro 6 standards, it balances high output with improved fuel efficiency over naturally aspirated predecessors.
| Parameter | Value | Source |
|---|---|---|
Displacement | 5,461 cc | |
Fuel type | Petrol (Unleaded, 95 RON min) | |
Configuration | 90° V8, DOHC, 32-valve | |
Aspiration | Twin-turbocharged | |
Bore × stroke | 98.0 mm × 90.5 mm | |
Power output | 325–368 kW (442–500 PS) | |
Torque | 700–800 Nm @ 2,000–4,000 rpm | |
Fuel system | CGI direct injection (up to 200 bar) | |
Emissions standard | Euro 6 | |
Compression ratio | 10.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Twin variable-vane turbochargers (hot-V configuration) | |
Timing system | Double-row roller chain (front-mounted) | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 228 kg |
The Mercedes-Benz M278.922 was used across Mercedes-Benz's W221/W213/X166 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-shortened intake manifolds in the GLS and revised cooling routing in the E-Class-and from 2014 the facelifted W221 models adopted updated fuel pump designs, creating 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 M278.922 delivers strong performance and refinement, but early models (2012–2013) had reliability concerns, particularly high-pressure fuel pump failures. Later revisions (post-2014) improved pump durability, so well-maintained examples can be robust. Regular servicing and using high-quality oil (5W-40 MB 229.51) greatly aid longevity.
The biggest issues are high-pressure fuel pump wear (leading to ticking noise or limp mode), intake carbon buildup, and turbo wastegate actuator sticking. Other concerns include oil leaks from valve covers and rear main seals. These are well-documented in Mercedes-Benz service bulletins.
This 5.5L twin-turbo petrol was used in several flagship models. It appeared in the S-Class (S500/S550), E-Class (E500/E550), GLS-Class (GLS500/GLS550), and CL-Class (CL500/CL550) between 2012 and 2017. All applications are Euro 6 compliant and feature longitudinal mounting.
Aftermarket ECU tuning is common on the M278922 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.
Moderate for a twin-turbo V8. In an S550 (W221), typical consumption is ~13.5 L/100km (city) and ~8.2 L/100km (highway), or about 21 mpg UK combined. Real-world figures depend heavily on driving style, but expect 19–23 mpg (UK) on mixed roads for a healthy M278.922.
Yes. The M278 series is an interference engine. If the timing chain fails or jumps, pistons can strike open valves, resulting in catastrophic engine damage. Chain and tensioner maintenance is critical—any abnormal noise should be investigated immediately.
Mercedes-Benz specifies a 5W-40 synthetic oil meeting MB 229.51 specification. Always use a high-quality oil suitable for turbocharged petrol engines and change it every 15,000 km or annually to ensure proper lubrication of the fuel pump and turbocharger.
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