The Mercedes — Benz M 254.923 is a 1,991 cc, inline — four turbocharged petrol engine produced between 2017 and 2023. It features a 350 bar direct injection system, twin — scroll turbocharger, and integrated starter — generator (ISG) enabling 48V mild — hybrid functionality. In standard tune, it delivers 190 kW (258 PS), with an additional 10 kW (14 PS) from the ISG, providing responsive acceleration and improved efficiency.
Fitted to the W205 C — Class, W222 S — Class, and X25…
All production years 2017–2023 meet Euro 6d-TEMP emissions standards (VCA UK Type Approval #VCA/EMS/5686).
The Mercedes-Benz M 254.923 is a 1,991 cc inline-four turbo petrol engine engineered for mid-to-large applications (2017–2023). It combines 48V mild-hybrid technology with direct injection to deliver responsive power and improved fuel efficiency. Designed to meet Euro 6d-TEMP standards, it balances performance with modern emissions requirements.
| Parameter | Value | Source |
|---|---|---|
Displacement | 1,991 cc | |
Fuel type | Petrol | |
Configuration | Inline-4, DOHC, 16-valve | |
Aspiration | Turbocharged | |
Bore × stroke | 83.0 mm × 92.0 mm | |
Power output | 190 kW (258 PS) @ 6,100 rpm (+10 kW ISG boost) | |
Torque | 400 Nm @ 3,000–4,000 rpm (+150 Nm ISG torque-fill) | |
Fuel system | Spray-guided direct injection (up to 350 bar) | |
Emissions standard | Euro 6d-TEMP | |
Compression ratio | 10.5:1 | |
Cooling system | Water-cooled | |
Turbocharger | Single twin-scroll turbocharger (BorgWarner), chargecooled | |
Timing system | Double-row roller chain (SOHC-style drive with DOHC cams) | |
Oil type | SAE 0W-40 MB 229.5 | |
Dry weight | 172 kg |
The Mercedes-Benz M 254.923 was used across Mercedes-Benz's W205, W222, and X253 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced engine mounts in the W222 and shortened accessory drives in the X253-and from 2020 the facelifted W205 models adopted revised intake manifolds and updated engine management, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The M 254.923's primary reliability risk is high-pressure fuel pump wear on early builds, with elevated incidence in high-mileage urban use. Internal Mercedes quality reports from 2021 noted a significant number of pre-2020 engines requiring fuel pump replacement before 120,000 km, while UK DVSA records indicate cooling system failures as a leading cause of overheating-related breakdowns. Extended service intervals and poor coolant maintenance increase wear and thermal stress, making fluid and oil discipline critical.
Analysis derived from Mercedes-Benz technical bulletins (2017-2023) and UK DVSA failure statistics (2019-2024). Repair procedures should follow manufacturer guidelines.
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The M 254.923 offers responsive performance but early models (2017-2020) are prone to high-pressure fuel pump issues if maintenance is delayed. Later units (post-2020) with reinforced pumps and updated controls are significantly more durable. When maintained with correct oil (0W-40 MB 229.5) and regular coolant service, these engines can reliably exceed 150,000 km.
Primary issues include high-pressure fuel pump failure (especially pre-2020), cooling system failures (water pump, thermostat), oil leaks from valve cover gaskets, and intake manifold runner binding. These are documented in Mercedes technical bulletins and field service reports from the late 2010s and early 2020s.
This 2.0L turbo inline-four was used in mid-range models: the W205 C-Class (C 300), W222 S-Class (S 350), and X253 GLC (GLC 300). Production spanned from 2017 to 2023, with minor updates in 2020 improving intake and engine management systems. It was not used in any other Mercedes or third-party vehicles.
Yes. ECU remapping can yield gains of 30-50 kW by optimizing boost, fuel, and ignition maps. Some owners add larger intercoolers and exhausts for further gains. However, the high-pressure fuel system and turbochargers are near their limits in stock form, so significant power increases require upgraded internals. Most tuning is done conservatively to maintain reliability.
Fuel consumption is moderate by modern standards. In the W205 C 300, typical usage is ~9.5 L/100km (city) and ~6.8 L/100km (highway), or about 41 mpg UK combined. Real-world figures depend on driving style, but expect 38-42 mpg (UK) in mixed conditions. Regular unleaded (RON 95) is sufficient for optimal performance.
Yes. The M 254 series is an interference engine. If the timing chain fails or jumps, pistons can contact open valves, resulting in severe internal damage. While chain durability is generally good, any signs of timing noise or wear should be investigated immediately to prevent catastrophic failure.
Mercedes specifies SAE 0W-40 oil meeting MB 229.5 specification. Use of high-quality synthetic oil is critical to protect the turbocharged valvetrain and maintain viscosity under high thermal load. Change intervals should not exceed 15,000 km or 24 months to prevent sludge and turbo degradation, especially in early production engines.
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