Overview & Design Features
The Infiniti OM651 is an inline four-cylinder, 2.1-liter (2143cc) turbocharged diesel engine, prominently featured in Infiniti’s European and select global markets. It represents a significant technological collaboration, being a Mercedes-Benz designed engine that Infiniti integrated into its vehicle lineup as part of a strategic partnership between Daimler AG and the Renault-Nissan Alliance. This engine allowed Infiniti to offer competitive diesel options, particularly in the premium compact executive and SUV segments, where diesel powerplants are highly sought after for their blend of fuel economy and torque output. Its introduction marked Infiniti’s commitment to expanding its market presence with diverse powertrain offerings.
Engineered for efficiency and robust performance, the OM651 features a cast-iron cylinder block for durability and an aluminum cylinder head to reduce overall weight. It employs a common rail direct injection system operating at pressures up to 2,000 bar (29,000 psi), utilizing advanced piezoelectric injectors for precise fuel delivery. Depending on the specific variant and vehicle application, the OM651 typically incorporates either a single variable geometry turbocharger (VGT) or a two-stage twin-turbocharger setup, optimizing boost response across the entire RPM range. The valvetrain consists of a double overhead camshaft (DOHC) configuration with four valves per cylinder, driven by a timing chain, ensuring efficient gas exchange and durability.
This engine was officially deployed in several Infiniti models, expanding their appeal in markets with a strong preference for diesel power. Key applications include the Infiniti Q50 (V37 chassis) from its launch in 2013, available in various trims offering different power outputs. It was also found in the Infiniti QX50 (J50 chassis), previously marketed as the Infiniti EX30d, particularly in European specification models. Production years generally align with the mid-2010s until market shifts reduced the demand for diesel engines in certain regions.
Technical Specifications
| Displacement (cc) | 2143 cc |
| Max Power (hp (kW) @ RPM) | 170 hp (125 kW) @ 3200-4200 RPM |
| Max Torque (Nm (kg*m) @ RPM) | 400 Nm (40.8 kg*m) @ 1600-2800 RPM |
| Fuel Type | Diesel |
| Fuel Consumption (l/100 km) | Approx. 4.8 – 5.5 l/100 km (combined cycle, varies by model) |
| Engine Type | Inline 4-cylinder, DOHC, Turbocharged Diesel |
| Compression Ratio | 16.2:1 |
| Cylinder Bore (mm) | 83.0 mm |
| Piston Stroke (mm) | 99.0 mm |
| Valvetrain | DOHC, Chain-driven |
| Valves per Cylinder | 4 |
| Additional Info | Common Rail Direct Injection, Piezoelectric Injectors, Variable Geometry Turbocharger (VGT), Diesel Particulate Filter (DPF), Exhaust Gas Recirculation (EGR) |
Common Problems & Reliability
While generally considered a robust and efficient engine, the Infiniti OM651, like many modern diesels, can exhibit specific issues, particularly at higher mileages. A notable concern in earlier versions involved the piezoelectric fuel injectors, which could fail, leading to misfires, rough running, or engine stalling. Later revisions of the injectors and updated software mitigated this issue significantly. Another common problem area is the Diesel Particulate Filter (DPF), which can become clogged, especially in vehicles frequently used for short journeys or city driving. DPF clogging can lead to reduced performance, increased fuel consumption, and warning lights. The Exhaust Gas Recirculation (EGR) valve is also prone to carbon buildup, restricting exhaust flow and potentially causing performance issues or emissions faults.
The timing chain system is designed to be “lifetime,” but stretching can occur at very high mileages (exceeding 200,000 km or 125,000 miles) if oil change intervals are neglected or incorrect oil is used. This can manifest as rattling noises from the engine and requires costly repair. With proper and diligent maintenance, including regular oil changes with specified lubricants, the OM651 engine is capable of achieving a realistic service life of 250,000 to 300,000 kilometers (approximately 155,000 to 185,000 miles) before requiring a major overhaul.
Maintenance Tips & Service Schedule
Adherence to a strict maintenance schedule is crucial for the longevity and reliability of the Infiniti OM651. Engine oil and filter changes should be performed every 15,000 to 20,000 kilometers (10,000 to 12,500 miles) or annually, whichever comes first. The use of a high-quality, low-SAPS (Sulphated Ash, Phosphorus, Sulphur) engine oil meeting ACEA C3 specification, typically a 5W-30 or 0W-30 viscosity, is mandatory to protect the DPF and other emissions components. The fuel filter requires replacement every 30,000 to 40,000 kilometers (18,000 to 25,000 miles) to prevent contamination of the high-pressure fuel system. The air filter should be changed every 40,000 to 60,000 kilometers (25,000 to 37,000 miles).
For the cooling system, a coolant flush and replacement is recommended every 5 years or 100,000 kilometers (60,000 miles). While the timing chain is designed for the engine’s life, vigilance for any unusual noises from the timing cover area at high mileage is prudent. Regular highway driving is essential to facilitate passive DPF regeneration and prevent premature clogging. Monitoring for diagnostic trouble codes (DTCs) related to the DPF, EGR, or fuel system via a professional scan tool can help identify potential issues before they become critical failures.
Conclusion
The Infiniti OM651 engine, a product of collaboration with Mercedes-Benz, offers a compelling balance of power, fuel efficiency, and refined performance within Infiniti’s luxury offerings. For a used vehicle buyer, it represents a generally reliable choice, provided the vehicle boasts a comprehensive and verifiable service history. Its inherent design and sophisticated components necessitate diligent maintenance with appropriate parts and lubricants. Buyers should prioritize examples that have received regular servicing and ideally have a history of varied driving conditions (not exclusively urban), which helps mitigate common diesel-specific issues like DPF and EGR valve problems. With proper care, the OM651 can provide many miles of economical and enjoyable driving.