How often should I change the spark plugs on my Subaru Forester?
For most Forester models with the common 2.5-liter engine, plan for spark plug changes roughly every 100,000 miles under normal driving. Turbocharged variants typically require changes around 60,000 miles. Driving conditions, plug type, and model year can shift these intervals.
Understanding the interval by engine and model year
Here is how the recommended replacement intervals typically break down for Forester models in recent generations. Always check your exact manual and confirm the plug type installed in your engine.
- Non-turbo 2.5L Forester (most generations): about 100,000 miles (160,000 km) under normal driving with iridium or platinum plugs.
- Turbocharged 2.0L Forester XT: about 60,000 miles (96,000 km); higher heat and load can shorten life, so many owners change around this interval.
- Severe driving conditions (short trips, dusty roads, towing, extreme temperatures): consider inspecting or replacing sooner, often around 60,000 miles or sooner based on condition.
Concluding: For the majority of Foresters with the standard 2.5L engine, long-life plugs can last up to 100,000 miles, while turbo variants generally require replacement closer to 60,000 miles. If you notice symptoms, don’t hesitate to check them sooner.
Signs that indicate it's time to change spark plugs
If you’re unsure whether the plugs are due, keep an eye out for these common indicators that wear or fouling is affecting performance.
- Rough idle or engine misfires, especially under load or at idle.
- Reduced acceleration or hesitation; overall drop in performance.
- Check Engine Light may come on with misfire codes (P0300-series) or cylinder-specific codes.
- Decreased fuel economy or higher emissions.
- Difficulty starting or repeated failed starts in cold weather or after short trips.
Concluding: If you notice any of these symptoms, have the plugs inspected and replaced as needed to maintain smooth running and efficiency.
What to expect during replacement
Most Foresters use long-life iridium or platinum plugs, which simplifies replacement but still requires correct parts, gap, and torque. Use the OEM-recommended plugs and, if necessary, replace ignition components such as coil packs or wires that show wear. Always follow the vehicle’s service manual for recommended torque and gap specifications to ensure proper seal and performance.
Summary
Bottom line: for most Subaru Forester models with the 2.5L engine, expect spark plug changes around 100,000 miles under normal driving. Turbocharged variants tend to need changes around 60,000 miles. Severe driving conditions can shorten the interval, and noticeable performance issues should prompt inspection sooner. Always consult your owner's manual for your specific year and model, and use OEM or OEM-equivalent plugs with the correct torque specs.
