How often should spark plugs be changed in a Subaru?
Most Subaru models with modern, long-life spark plugs are designed to go about 100,000 miles between changes under normal driving; turbocharged variants typically require replacement around 60,000 miles. Always verify the exact interval in your owner’s manual for your engine code and model year.
Understanding the intervals
Subaru’s official guidance varies by engine family and drivetrain. The sections below lay out the typical schedules you’ll encounter in service manuals and owner manuals, along with caveats that can affect timing.
Non-turbo and most modern Subaru engines
Non-turbo Subaru engines, including the FA/FB series, commonly use iridium or platinum plugs rated for roughly 100,000 miles under normal driving conditions. Real-world mileage can differ based on driving style, climate, and fuel quality, so many owners replace around the 90,000–110,000 mile mark.
Typical interval guidance (non-turbo):
- Non-turbo / naturally aspirated engines: around 100,000 miles (about 160,000 km) under normal driving
- Consult the exact interval in your vehicle’s owner's manual for your engine code
Concluding note: Always refer to the specific model’s service schedule and ignition system guidelines provided by Subaru for your engine code.
Turbocharged and performance-oriented models
Turbocharged Subaru engines, such as those in WRX and STI variants, experience higher heat and load, which typically leads to a shorter spark plug interval. Factory guidance commonly places replacement around 60,000 miles, though exact numbers can vary by engine code (for example FA20/FA24 variants) and model year.
Typical interval guidance (turbo):
- Turbocharged engines: approximately 60,000 miles, with some models ranging up to 60–100,000 miles depending on design and conditions
Concluding note: Always verify the official maintenance schedule for your exact engine and year, and consider more frequent checks if you drive aggressively, tow heavy loads, or frequently do short trips.
Other factors that affect spark plug replacement timing
Beyond the base interval, several conditions can accelerate wear or delay replacement. Short trips, frequent cold starts, heavy towing, poor fuel quality, and aging ignition coils can all affect when plugs should be changed. Carbon buildup with direct-injection engines and misfire symptoms should prompt an inspection even if you’re below the general mileage guideline.
- Driving conditions: predominantly short trips, stop-and-go traffic, or heavy load
- Engine design: turbocharged versus naturally aspirated, direct injection considerations
- Maintenance quality: oil changes, air filter, and coil health
- Symptom indicators: rough idle, misfires, power loss, reduced fuel economy
Concluding note: A regular diagnostic check during routine maintenance helps ensure you don’t miss signs of impending plug wear.
Practical steps for Subaru owners
To keep your Subaru running smoothly, follow these practical steps in addition to the mileage-based schedule:
- Consult the owner’s manual for your exact engine code and year-specific interval
- Use OEM or high-quality replacement plugs suitable for your engine
- Have plugs installed by a qualified technician to proper torque and gap specs
- Monitor for signs of wear such as rough running or reduced fuel economy
Conclusion: If in doubt, schedule a plug inspection during the next maintenance visit and plan replacement around the published interval, adjusting for your driving style and climate.
Summary
For most Subaru models with modern long-life plugs, plan for replacement around 100,000 miles under normal driving; turbocharged models typically around 60,000 miles. Always verify the exact interval in your owner's manual for your engine code and driving conditions, and consider more frequent checks if you drive aggressively, tow, or do a lot of short trips. Regular inspection and using quality plugs will help maintain performance and fuel efficiency.
