What size spark plugs for Subaru Forester XT?
Forester XT spark plug sizing depends on the exact engine and model year, but most turbo versions use 14 mm threaded plugs with a small gap around 0.028–0.032 inches, and a one-step colder heat range for turbo operation.
The Forester XT has appeared with different engines across generations, including the EJ25 2.5L turbo in older models and the FA20 2.0L turbo in newer ones. Because plug dimensions and gaps are engine-specific, always verify your exact year and engine code in the owner's manual or Subaru service data to confirm heat range, reach, and gap.
Overview by engine variant
EJ25 turbo (older Forester XT, approx. 2004–2007)
For this engine family, spark plugs are typically 14 mm in diameter. A common gap range is roughly 0.028–0.032 inches, with a heat range one step colder than a naturally aspirated version to cope with turbo boost. Iridium or platinum plugs from major brands (e.g., NGK or Denso) are frequently recommended. Always confirm the exact part number and reach from the official service data for your specific year and VIN.
Note: Torque specs and installation practices (such as anti-seize and torque direction) come from the official service manual for your vehicle; follow those guidelines to ensure proper seating and heat dissipation.
FA20 turbo (modern Forester XT, roughly 2014–present in many markets)
The current turbo-equipped Forester XT typically uses a 14 mm spark plug with a small gap, commonly around 0.026–0.032 inches. The heat range is usually one step colder than stock for turbo operation, and iridium or platinum plugs are standard choices. Exact plug part numbers and reach should be verified in the Subaru parts catalog or service manual for your year and engine code (FA20F).
Because the FA20 is direct-injected and turbocharged, some variations exist by market and sub-model, so checking the specific guide for your vehicle is important before purchasing plugs.
What to check before buying spark plugs
Before selecting plugs, verify these details to avoid mismatches that could affect performance or reliability.
- Engine code and model year (e.g., EJ25D vs. FA20F) and whether the vehicle is turbocharged.
- Recommended heat range and gap from the official Subaru service data.
- Thread size and reach (most Subaru turbo engines use 14 mm threads with varying reach; verify for your exact year).
- Preferred brands and plug type (iridium or platinum are common for modern Subarus; avoid copper plugs in direct-injected turbo engines except as specified).
Correctly identifying these details helps ensure you select the right plug and avoid misfires or fouling in turbo applications.
Common plug options used with Subaru Forester XT
Across generations, Subaru enthusiasts and service manuals tend to favor these general guidelines, though exact part numbers should be confirmed for your vehicle:
- Fourteen-millimeter thread plugs are standard for most Forester XT turbo engines.
- Iridium or platinum center electrodes are preferred for longevity and reliable cold-start performance in turbo applications.
- Gap typically sits in a tight range around 0.026–0.032 inches, with adjustments based on engine tuning and market-specific specs.
- Check that the heat range is one step colder than a naturally aspirated version to help manage turbo boost temperatures.
Following these guidelines and confirming with your precise model data will help you choose plugs that maximize performance and reliability.
Summary
In short, the spark plug size for a Subaru Forester XT is largely determined by the engine version and year. Most turbo models use 14 mm threaded plugs with a small gap in the 0.026–0.032 inch range and a one-step colder heat range. Always verify the exact specifications in the owner’s manual or Subaru service data for your specific year and engine code to ensure you pick the correct plug type, reach, and gap. If in doubt, consult a Subaru technician or the official parts catalog to confirm the precise part numbers for your vehicle.
