Subaru H4 Engine Specifications
The Subaru H4 engine, also known as the Subaru flat-four engine, is a hallmark of the brand’s engineering prowess. This engine configuration is known for its unique design and performance characteristics. Below is a detailed overview of its specifications.
| Specification | Details |
|---|---|
| Engine Type | Horizontally Opposed 4-Cylinder (H4) |
| Displacement | 2.0L, 2.5L, and 2.4L |
| Fuel System | Multi-Point Fuel Injection (MPFI) |
| Power Output | 152 – 260 hp (varies by model and year) |
| Torque | 145 – 277 lb-ft (varies by model and year) |
| Compression Ratio | 10.0:1 to 12.5:1 (varies by model and year) |
| Valvetrain | DOHC with AVCS (Active Valve Control System) |
| Fuel Type | Regular Unleaded (87 octane) or Premium (91 octane) |
| Cooling System | Liquid-cooled |
Engine Configuration
The Subaru H4 engine features a horizontally opposed configuration, which is often referred to as a “boxer” engine. This design offers several advantages:
- Lower Center of Gravity: The flat design helps lower the vehicle’s center of gravity, enhancing stability and handling.
- Reduced Vibration: The opposing pistons balance each other, resulting in smoother operation and less vibration.
- Compact Size: The engine’s layout allows for a more compact engine bay, which can improve vehicle design and aerodynamics.
The H4 engine is typically paired with Subaru’s signature all-wheel-drive system, making it a popular choice for various models, including the Subaru Impreza, Legacy, and Outback.
Performance Characteristics
The performance of the Subaru H4 engine can vary significantly depending on the specific model and year. Key characteristics include:
- Acceleration: The engine provides responsive acceleration, particularly in turbocharged variants.
- Fuel Efficiency: Generally, the H4 engine offers good fuel economy, especially in naturally aspirated versions.
- Turbocharged Options: Turbo variants deliver higher power and torque, catering to performance enthusiasts.
Engine Oil Specifications
Proper engine oil is crucial for maintaining the performance and longevity of the Subaru H4 engine. Below are the recommended oil specifications.
| Specification | Details |
|---|---|
| Oil Type | Synthetic or Conventional |
| Viscosity Grade | 5W-30 or 0W-20 (varies by model and climate) |
| Oil Capacity (with filter) | 5.1 – 6.9 quarts (varies by model) |
| Oil Change Interval | 6,000 miles or 6 months (whichever comes first) |
Service Intervals
Regular maintenance is essential for the optimal performance of the Subaru H4 engine. Below are the recommended service intervals:
Regular Maintenance Schedule
- Oil Change: Every 6,000 miles or 6 months.
- Air Filter Replacement: Every 15,000 to 30,000 miles, depending on driving conditions.
- Spark Plug Replacement: Every 60,000 miles.
- Coolant Flush: Every 30,000 miles.
- Transmission Fluid Change: Every 30,000 to 60,000 miles.
Additional Considerations
When servicing the Subaru H4 engine, consider the following:
- Use Genuine Subaru Parts: For optimal performance and reliability, use OEM parts.
- Monitor Fluid Levels: Regularly check oil, coolant, and transmission fluid levels.
- Listen for Unusual Noises: Any strange sounds from the engine may indicate a need for inspection.
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Conclusion
The Subaru H4 engine is a well-engineered powerplant that combines performance, efficiency, and reliability. Understanding its specifications, configuration, oil requirements, and service intervals is essential for maintaining its longevity and performance. Regular maintenance and proper care will ensure that your Subaru continues to deliver the driving experience it is known for.
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