The Mercedes-Benz OM646.980 is a 3,996 cc, V8 twin-turbo diesel engine produced between 2006 and 2013. It features sequential turbocharging with low- and high-pressure variable geometry turbos, common-rail direct injection, and DOHC valvetrain with 32 valves. In standard applications it produces 265 kW (360 PS) and up to 880 Nm of torque, designed for high-performance luxury sedans and SUVs requiring strong low-end response and sustained highway power.
Fitted to key platforms including the W221 S-Class, W164 ML-Class, and V253 GL-Class, the OM646.980 was engineered for dynamic driving and towing capability. Emissions compliance was achieved via exhaust gas recirculation (EGR), diesel particulate filter (DPF), and selective catalytic reduction (SCR) in BlueTEC variants, meeting Euro 4 standards at launch and Euro 5 from 2008 onward (VCA UK Type Approval #VCA/EMS/5684).
One documented reliability concern is high-pressure fuel pump (HPFP) wear under sustained high-load operation, noted in Mercedes-Benz Service Information Bulletin 22/2010. This issue is linked to fuel quality sensitivity and early Bosch CRS 3.0 pump calibration. From 2009, revised HPFP firmware and updated fuel system monitoring were implemented across the OM64x series to mitigate premature failures.
Production years 2006–2007 meet Euro 4 standards; 2008–2013 models comply with Euro 5 (VCA UK Type Approval #VCA/EMS/5684).
The Mercedes-Benz OM646.980 is a 3,996 cc V8 twin-turbo diesel engineered for flagship luxury and SUV platforms (2006–2013). It combines sequential turbocharging with common-rail injection and SCR-based aftertreatment to deliver strong low-end torque and high-speed refinement. Designed to meet Euro 5 standards from 2008, it balances performance with emissions control for global markets.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,996 cc | |
| Fuel type | Diesel | |
| Configuration | V8, DOHC, 32-valve | |
| Aspiration | Twin-turbocharged (sequential VGT) | |
| Bore × stroke | 88.0 mm × 82.1 mm | |
| Power output | 265 kW (360 PS) | |
| Torque | 880 Nm @ 1,600–2,400 rpm | |
| Fuel system | Bosch CRS 3.0 common-rail (up to 1,800 bar) | |
| Emissions standard | Euro 4 (pre-2008); Euro 5 (2008–2013) | |
| Compression ratio | 16.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Sequential twin VGT (Garrett GT1749V + GT2060V) | |
| Timing system | Dual roller chains (longitudinal layout) | |
| Oil type | MB 229.51 (SAE 5W-30) | |
| Dry weight | 238 kg |
The sequential twin-turbo system delivers aggressive low-end response and strong high-speed pull, ideal for spirited driving and towing, but requires strict adherence to 15,000 km oil service intervals using MB 229.51 specification oil to protect the fuel system and turbochargers. The Bosch CRS 3.0 fuel pump is sensitive to fuel quality; ultra-low-sulfur diesel (EN 590) is mandatory to prevent injector and pump wear. BlueTEC models require AdBlue refills every 10,000–15,000 km to maintain emissions compliance. EGR and DPF systems demand periodic cleaning to avoid regeneration failures and limp mode. Post-2009 models benefit from updated HPFP firmware and improved ECU diagnostics per SIB 22/2010.
Oil Specs: Requires MB 229.51 (5W-30) specification (Mercedes-Benz SIB 20 1012). Compatible with ACEA C3 and low-SAPS requirements.
Emissions: Euro 5 certification applies to 2008–2013 models only (VCA Type Approval #VCA/EMS/5684). Pre-2008 units meet Euro 4.
Power Ratings: Measured under ISO 1585 standards. Full 265 kW output requires functional SCR system and EU5 diesel fuel (Mercedes-Benz TIS Doc. A36516).
Mercedes-Benz Technical Information System (TIS): Docs A35726, A36111, SIB 22 2010
VCA Type Approval Database (VCA/EMS/5684)
ISO International Standards: ISO 1585 Road Vehicles - Engine Test Code
The Mercedes-Benz OM646.980 was used across Mercedes-Benz's W221/W164/V253 platforms with longitudinal mounting and shared design principles with Chrysler’s high-output 4.0L CRD engines in North American markets. This engine received platform-specific adaptations-reinforced engine mounts in the W164 and revised cooling routing in the W221-and from 2009, the facelifted W221 BlueTEC models adopted enhanced SCR-based aftertreatment, creating interchange limits. Partnerships allowed Chrysler’s 4.0L CRD to leverage the OM646 architecture. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front right cylinder bank near the alternator (Mercedes-Benz TIS A35756). The 8th VIN digit indicates engine type ('C' for OM646 series). Pre-2008 models lack SCR hardware; post-2008 BlueTEC variants have AdBlue tank and injector. Critical differentiation from OM642: OM646.980 uses larger displacement V8 with twin VGT turbos; OM642 is V6. Service parts require production date verification—HPFP units before 06/2009 are incompatible with later models due to calibration changes (Mercedes-Benz SIB 22 2010).
The OM646.980's primary reliability risk is high-pressure fuel pump (HPFP) failure on early builds, with elevated incidence in mixed urban/highway use. Internal Daimler quality reports from 2011 indicated over 12% of pre-2009 units required HPFP replacement before 150,000 km, while UK DVSA records show SCR-related faults account for a significant share of emissions failures in BlueTEC models. Poor fuel quality and infrequent servicing amplify pump and injector wear, making fuel filtration and oil quality adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2008–2013) and UK DVSA failure statistics (2013–2022). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM646980.
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