Parts for your 2017 Subaru Forester-Spark plugs

2017 Subaru Forester spark plugs — what they do and when to replace them

Yes, spark plugs are relevant for the 2017 Subaru Forester models with petrol engines (the 2.5L FB25 and the 2.0L turbo FA20F). These engines use long-life iridium plugs. If the vehicle is the 2.0D turbo-diesel variant offered in some markets, it does not use spark plugs at all — diesels rely on compression ignition and use glow plugs for cold starts instead. This position aligns with Subaru’s 2017 Forester Owner’s Manual and maintenance schedule, the Subaru factory service literature for FB/FA engines, and fitment data from major plug makers (NGK and Denso).

For petrol Foresters, spark plugs sit at the heart of efficient combustion. Each plug delivers a precisely timed spark to light the air–fuel mix, keeping the flat-four humming smoothly, helping fuel economy, and keeping emissions in check. Iridium tips resist wear and hold their gap longer than old copper styles, which is why Subaru specifies them from factory.

As part of regular servicing, it’s smart to plan plug replacement at the interval Subaru sets for the specific engine and market conditions. As a practical guide, many workshops in Australia and New Zealand service 2017 Foresters at about 60,000–100,000 km (shorter intervals for the 2.0XT turbo). Always confirm against the vehicle’s maintenance schedule and under‑bonnet labels.

Signs the plugs are getting tired include:

• Hard starting, rough idle, or a stumble under load
• Higher fuel use and a lazier throttle feel
• Misfire codes or a flashing check engine light

When it’s time, replace all four plugs as a set. Genuine or OEM-equivalent iridium plugs from recognised brands match Subaru’s heat range and reach. On these boxer engines, access is tighter than a typical inline-four, so expect to move the air box or battery for room. A few workshop tips drawn from Subaru service procedures and NGK/Denso guidance:

• Only install on a cool engine and blow debris from plug wells first
• Plugs arrive pre‑gapped — avoid regapping iridium tips
• Do not use anti‑seize on modern, nickel-plated threads, torque to the factory spec with a torque wrench
• Inspect coil boots, use a smear of dielectric grease, and clear any oil from the tubes (a sign cam cover tube seals may need attention)

Looked after this way, a 2017 Forester keeps its smooth idle, crisp response, and proper fuel economy. If in doubt, a Subaru-trained tech can check live misfire data and advise the ideal interval for local conditions.

Popular questions about 2017 Subaru Forester spark plugs

Which spark plugs does a 2017 Subaru Forester use?
The petrol 2.5i and 2.0XT engines use long‑life iridium spark plugs matched to Subaru’s specified heat range and thread reach. The exact part depends on engine code and build month, so it’s best to match by VIN or engine code with OEM or equivalent NGK/Denso options.
If the vehicle is the 2.0D diesel, it uses glow plugs — not spark plugs.

How often should the plugs be changed?
Most petrol 2017 Foresters in AU/NZ are serviced around the 60,000–100,000 km mark for plugs, with the turbo 2.0XT typically on the shorter end. Check the maintenance schedule in the owner’s manual for the exact interval for that engine and usage.

Can a home mechanic replace them?
Yes, with patience and the right tools. The boxer layout means working space is tight, so wobble extensions help and the air box or battery may need to be moved. Always follow the correct torque spec and avoid anti‑seize on plated plugs. If unsure, letting a pro handle it avoids cross‑threading the alloy heads.