When should Subaru spark plugs be replaced?
Most Subaru engines that use iridium or platinum-tipped plugs are designed to go about 100,000 miles before replacement. Copper-core plugs typically wear faster and are commonly replaced around 30,000 miles. Turbocharged Subarus usually require closer attention and may need replacement around 60,000 miles or sooner, depending on driving conditions. Always check your owner’s manual or with a Subaru dealer for the exact interval for your model and year.
Understanding plug types and general replacement intervals
Different spark plug materials wear at different rates, and engine design influences how long a plug lasts. Here is a practical guide to what you might expect by plug type.
- Copper-core plugs: typically around 30,000 miles (about 48,000 km) in many Subaru models, sometimes shorter in aggressive driving or harsh conditions.
- Platinum or iridium plugs: commonly 60,000 to 100,000 miles (96,000 to 160,000 km), with many modern Subarus leaning toward the 100,000‑mile mark.
- Turbocharged and high-heat engines: replacement intervals are often shorter, commonly around 60,000 miles or less, especially with hard driving or frequent short trips.
Note: Some older Subarus used copper plugs with shorter service intervals. Always verify the exact recommendation for your year and engine by consulting the owner's manual or a Subaru service advisor, as driving style and environment can shorten or extend these intervals.
Model and engine-specific guidance
Interval recommendations vary by engine family and whether the vehicle is naturally aspirated or turbocharged. The following guidance reflects typical ranges, but you should confirm the exact figure for your year and engine code.
Non-turbo engines (FA/FB family)
In many non-turbo FA/FB engines, iridium or platinum plugs are commonly rated for around 100,000 miles, while copper plugs may require replacement much sooner, often around 30,000 miles depending on use and heat range.
- FA/FB 2.0L and 2.5L configurations: iridium/platinum plugs often specified at about 100,000 miles; copper plugs around 30,000 miles.
Always check the specific model-year manual for the exact interval, as Subaru occasionally updates recommendations by engine code.
Turbocharged models (WRX, STI, some Forester/XV variants)
Turbo engines operate at higher temperatures and stresses, so plug wear can be accelerated. Replacement intervals are typically shorter and often cited around 60,000 miles or less, with some drivers replacing as early as 30,000 miles under aggressive driving or frequent short trips.
- WRX/STI and other turbo-equipped Subarus: typical guidance around 60,000 miles; consult the manual for the precise figure for your year and engine.
If you tow, drive in extreme conditions, or rack up a lot of short trips, consider inspecting plugs sooner and adhering to the service schedule in your manual or by a Subaru technician.
Signs that indicate it may be time to replace spark plugs
Beyond the official intervals, several symptoms can signal worn or fouled plugs. Watch for these indicators and have the ignition system checked if they appear.
- Rough idle, misfires, or hesitation during acceleration
- Reduced fuel economy or noticeably weaker performance
- Hard starting or longer cranking times
- Check Engine Light with misfire or ignition-related codes
- Visible wear or damage to old plugs upon inspection
If you notice any of these symptoms, it's a good idea to have the plugs inspected and replaced if necessary to protect engine efficiency and reliability.
Summary
For most modern Subarus, plan spark plug replacement around 100,000 miles if your plugs are iridium or platinum. Copper-core plugs typically require earlier replacement, around 30,000 miles. Turbocharged models often need service closer to 60,000 miles or sooner depending on driving patterns and conditions. Always refer to your specific owner's manual for the exact interval, and consider driving style and climate when estimating replacement timing. If in doubt, have a qualified Subaru technician inspect and replace the plugs to maintain optimal performance and fuel efficiency.
Additional note
To stay on track, keep a maintenance log and set reminders aligned with your model’s recommended interval. Subaru’s service bulletins and dealer guidance can provide model-year specific nuances that improve reliability and efficiency.
