Parts for your 2008 Subaru Forester-Spark plugs

2008 Subaru Forester spark plugs — what they do and when to replace them

Yes, a 2008 Subaru Forester uses spark plugs on its petrol engines. That’s backed by the Subaru Owner’s Manual and workshop information for MY08 Forester, Subaru Australia/NZ maintenance schedules, and NGK/Denso application catalogues. Only diesel variants use glow plugs, those arrived later in AU/NZ and aren’t typical for 2008 models here.

On a petrol Forester, spark plugs are the tiny workhorses that ignite the air–fuel mix in the boxer engine. Every time the driver taps the throttle, the plugs deliver a precise spark that keeps combustion clean, power smooth, fuel use sensible and emissions in check. When they’re tired or fouled, the engine can feel a bit lazy, burn more fuel and throw a misfire light.

For most 2008 Forester petrol models running long‑life iridium or platinum plugs, replacement is commonly due around 100,000 km under normal driving. Turbocharged variants often benefit from shorter intervals (about 60,000–75,000 km) because they run hotter and place more demand on the ignition system. Always match the interval to the logbook and the under‑bonnet label for the exact engine code.

Signs the Forester’s plugs are ready for attention include:

• Hard starting, rough idle, or a stumble under load
• Higher fuel use and sluggish acceleration
• Check engine light for misfire codes

Good workshop practice keeps things sweet under the bonnet:

• Use the specified plug type and heat range (OE‑equivalent iridium is a safe bet).
• Most iridium plugs are pre‑gapped, avoid forcing the fine centre electrode. Check against the label/manual if you do measure.
• Install into a cool aluminium head with a torque wrench, typical 14 mm gasketed plugs are around 18–25 Nm, but the Subaru spec takes priority.
• Don’t add anti‑seize to modern nickel‑plated plug threads, it can alter torque and lead to over‑tightening.
• Inspect coil boots (or leads, if fitted) for cracks and carbon tracking, replace any brittle bits while you’re there.

Access on the flat‑four can be a bit tight, so if skinned knuckles aren’t your thing, a proper service bay and the right wobble extensions make the job painless. As part of regular servicing, fresh plugs help a 2008 Forester start crisply on frosty mornings, pull cleanly up hills and keep emissions gear happy for the long haul.

Popular questions about 2008 Subaru Forester spark plugs

What type of spark plug is best for a 2008 Forester?
An OE‑equivalent iridium plug is ideal for longevity and stable spark, especially on the 2.5‑litre petrol engines. Quality brands listing to Subaru spec will give the right heat range, reach and tip design. Turbo models should stick closely to the factory‑specified plug.

How often should the plugs be changed in Australia or New Zealand?
Expect roughly 100,000 km for iridium‑equipped non‑turbo engines. Turbo variants are often serviced sooner, around 60,000–75,000 km. If the vehicle tows, does lots of short trips, or feels off‑song, bring the interval forward and check condition.

What’s the correct plug gap and torque?
Many OE‑style iridium plugs come pre‑gapped near the Subaru spec (commonly around 0.7–0.8 mm). Avoid bending the fine tip unless the manual requires it. Torque typically sits about 18–25 Nm for 14 mm gasketed plugs in an aluminium head—always follow the Subaru workshop specification for the exact engine.