Which Subaru Forester engine is most reliable?

The naturally aspirated 2.5-liter flat-four (the FB25) is generally regarded as the most reliable Forester engine, especially in non-turbo models.

To understand this, it helps to trace the Forester’s engine lineup across generations. Subaru moved from older EJ-series engines to the modern FA/FB family, while occasional turbo and larger-displacement options offered different trade-offs. Reliability can depend on model year, maintenance history, and how hard the engine is worked, but the FB25 NA engine has earned a reputation for steady, low-stress operation and fewer turbo-related or high-mileage issues.

Engine options and reliability overview

Here is a snapshot of the main engine options that have powered the Forester in recent years and how they are generally perceived for reliability.

• FB25 2.5L naturally aspirated (NA): The preferred choice for reliability in most non-turbo Foresters. It’s mechanically simpler than turbo variants, with a long track record of solid longevity when properly maintained. Regular maintenance remains key to avoiding aging-related problems.


• FA20/FA20D 2.0L turbo: Provides strong performance but carries more maintenance points (turbo components, oil supply, intercooling). In practice, turbo Foresters can be reliable, but they pose higher risk of oil consumption and turbo-related failures if maintenance lags or cooling and oil systems aren’t kept in good shape.


• EJ25 2.5L (older generation, non-turbo): Historically more prone to head gasket failures and related cooling issues at higher mileage. Reliability tends to be lower than the modern FB25, especially if routine maintenance has been inconsistent.


• EZ36 3.6L H6 (less common in Forester): Smooth and robust when well maintained, but heavier and more expensive to service. Reliability is generally good, though fewer model years and higher repair costs mean some owners opt for smaller, simpler engines.

Conclusion: Across the Forester lineup, the FB25 NA engine stands out as the most reliable default choice. Turbo options and older EJ-based engines bring more potential maintenance demands or failure points, though they can be perfectly reliable with meticulous care and timely service.

Maintenance practices that maximize Forester engine reliability

Adhering to a diligent maintenance routine is crucial for getting the longest life from any Forester engine. The following practices are widely recommended by technicians and reliability surveys to minimize common failure points.

1. Follow the manufacturer’s maintenance schedule, including regular oil changes using the recommended grade and viscosity (often synthetic 0W-20 for many models) and timely replacement of filters.


2. Keep the cooling system in good shape: monitor coolant levels, replace coolant at recommended intervals, and inspect hoses, the thermostat, and the water pump for wear or leaks.


3. Use quality parts and fluids, and if you have a turbo model, use turbo-specific oils and parts as recommended by Subaru.


4. Address recalls and service bulletins promptly; fix any leaks, misfires, or sensor issues early to prevent cascading problems.


5. Be vigilant for symptoms such as unusual oil consumption, rising exhaust smoke, or coolant/oil mixing, and have a qualified mechanic diagnose potential head gasket or turbo issues sooner rather than later.

Conclusion: A consistent maintenance routine and choosing a well-documented engine (preferably the FB25 NA) are key steps toward long-term reliability in a Subaru Forester.

Bottom line

For most buyers prioritizing reliability, a Forester equipped with the FB25 2.5L naturally aspirated engine, paired with thorough maintenance history, is the safest bet. Turbocharged or older EJ-based engines can be reliable with diligent care, but they carry higher risk and maintenance demands. When shopping used, prioritize documented service history, evidence of cooling system upkeep, and a clean record of head gasket-related repairs on older engines.

Summary

In summary, the FB25 2.5L naturally aspirated engine is the Forester’s most reliable option overall, especially for drivers seeking lower maintenance risk. Turbocharged and older EJ-series engines may offer advantages in power or legacy appeal but typically demand more careful upkeep and attention to cooling, oil, and turbo components. A well-maintained, non-turbo FB25 Forester from recent years represents the strongest reliability profile for most buyers.