Parts for your 2009 Subaru Forester-Spark plugs

2009 Subaru Forester Spark Plugs

Based on technical sources including the 2009 Subaru Forester Owner’s Manual and Subaru Service Manual, plus AU/NZ application guides from NGK and Denso, spark plugs are fitted to all 2009 Forester petrol models (2.5i EJ253 and turbocharged XT EJ255). Only the 2.0D diesel variant (sold in select markets) does not use spark plugs, it uses glow plugs, as diesel combustion relies on compression ignition rather than a spark.

For petrol 2009 Foresters, spark plugs are a small part with a big job. They ignite the air–fuel mix inside the boxer engine’s cylinders, keeping starts crisp, idle smooth, power on tap, fuel economy tidy, and emissions in check. Subaru specifies long-life iridium or platinum plugs for this model, chosen for durability and stable spark at higher temperatures—handy for Aussie and Kiwi conditions and for the XT’s turbo heat.

As part of regular servicing, replacement intervals typically fall around 100,000 km for the naturally aspirated 2.5i and shorter for the XT turbo (often around 60,000 km), per Subaru schedules for this generation. Workshop practices vary, so it pays to confirm the exact interval in the owner’s manual or a trusted AU/NZ service schedule. Checking plug condition during major services is smart: look for worn electrodes, heavy deposits, oil fouling, or cracked insulators.

Fit quality OEM-spec plugs from reputable brands (NGK or Denso are common for Subaru). Iridium plugs are pre-gapped and generally shouldn’t be re-gapped, if a check is needed, the spec for these EJ25 engines is typically in the 0.7–0.8 mm range. Install into a cool engine, use a new crush washer, and tighten to the correct torque (around 18–25 N·m for 14 mm gasket-seat plugs unless the plug maker specifies otherwise). Most plug makers advise against anti-seize on modern, nickel-plated shells, as it can lead to over-tightening.

Because the Forester’s horizontally opposed engine tucks the plugs low and tight, access is snug. A thin-wall spark plug socket, wobble extension, and a torque wrench make life easier. If time-poor or unsure, a professional service is well worth it—especially on the turbo XT where heat and load are higher.

• Common signs they’re due: rough idle, sluggish acceleration, misfires under load, harder starts, and rising fuel use.
• Good habits: replace ignition leads or coil boots if cracked, keep water and cleaners away from connectors, and fix oil leaks that can foul plugs.

Popular questions about 2009 Subaru Forester spark plugs

Does a 2009 Subaru Forester use spark plugs?
The petrol 2.5i and XT models do use spark plugs. Only the 2.0D diesel (where offered) doesn’t—it uses glow plugs because diesels ignite fuel by compression, not a spark.

How often should they be replaced?
For most 2.5i petrol models, expect around 100,000 km with quality iridium plugs, the XT turbo is usually shorter, often around 60,000 km. Always check the service book for the exact schedule used in Australia or New Zealand.

What type should be fitted?
Use OEM-equivalent iridium or platinum plugs from reputable brands. Heat range and part numbers differ between 2.5i and XT, so match to the engine code and build date listed in the owner’s manual or a trusted AU/NZ parts guide.