Parts for your 2015 Subaru Forester-Spark plugs

2015 Subaru Forester spark plugs – what they do and when to change them

For the 2015 Subaru Forester, spark plugs are absolutely relevant on the petrol models (2.0i and 2.5i, plus the 2.0 XT turbo). Subaru’s Owner’s Manual and scheduled maintenance guides for this model year specify spark plug types and service intervals for these engines. By contrast, the 2.0D diesel variant does not use spark plugs at all, as a compression-ignition engine it relies on glow plugs for cold starts, a point confirmed in Subaru service literature and common diesel engine design references. Parts catalogues from NGK and Denso also list iridium spark plugs for the 2015 Forester petrol engines, further verifying fitment.

Spark plugs are the tiny but crucial parts that ignite the air–fuel mix inside the Forester’s petrol engine. Each plug fires thousands of times a minute, and modern iridium designs used by Subaru deliver a strong, consistent spark with minimal wear. That reliable spark helps the FB-series and FA-series engines start cleanly, idle smoothly and sip less fuel—handy for both city runs and long Kiwi or Aussie road trips.

As part of regular servicing, it’s smart to plan spark plug replacement roughly around 100,000 km for the 2.0i/2.5i petrol models, and earlier for the 2.0 XT turbo or if the vehicle sees lots of short trips, towing or dusty conditions. Subaru’s market-specific maintenance schedule should be followed for the final word. When fitting new plugs, stick with OEM-grade iridium from reputable makers, and avoid regapping fine-wire iridium tips. A technician will usually install them on a cool engine, torque them correctly (Subaru service data specifies a light torque for the alloy heads), and check ignition coils and boots while they’re in there.

• Replace all four plugs as a set to keep the engine balanced.
• Use the exact heat range and design specified by Subaru, performance “upgrades” can cause misfires or pre-ignition.
• Don’t use anti-seize on plated plug threads unless the manufacturer explicitly allows it, it can alter torque readings.
• Watch for tell-tales like rough idle, sluggish take-off, higher fuel use, or a check-engine light—these can point to worn plugs.
• Combine plug replacement with a general engine health check: coils, air filter, and PCV inspection.

Done on time and done right, fresh plugs keep the 2015 Forester feeling lively, help emissions equipment stay happy, and can save a few dollars at the bowser over the long haul.

FAQs

How often should spark plugs be replaced on a 2015 Subaru Forester?
The petrol models typically go around 100,000 km on their iridium plugs under normal use. Turbo models or vehicles driven in harsher conditions may need them sooner. Always check the Subaru maintenance schedule for your market and engine code.

What type of spark plug does the 2015 Forester use?
Subaru specifies fine-wire iridium plugs for the petrol engines. Use OEM-equivalent NGK or Denso part numbers listed in Subaru documentation or reputable catalogues. They arrive pre-gapped and shouldn’t be adjusted unless the manufacturer allows it.

What are the signs my Forester’s spark plugs need attention?
Hard starting, rough idle, hesitation under load, increased fuel use, or a flashing/misfire check-engine light are common clues. If coils and leads check out, aged plugs are often the culprit.