Parts for your 2010 Subaru Impreza-Spark plugs

2010 Subaru Impreza spark plugs: what they do and when to replace them

For the 2010 Subaru Impreza sold in Australia and New Zealand, spark plugs are relevant and fitted to the common petrol (gasoline) variants, including the EJ-series engines found in 2.0 and 2.5 models and WRX trims. Only the Euro‑market 2.0D diesel (rare in ANZ) does not use spark plugs, relying on compression ignition and glow plugs instead. This position is supported by the Subaru Owner’s Manual and Warranty & Maintenance Booklet for MY2010 Impreza, Subaru service manual ignition specifications for EJ engines, and ANZ application catalogues from ignition manufacturers such as NGK and Denso.

On the petrol Impreza, spark plugs ignite the fuel‑air mix in each cylinder. Healthy plugs help the boxer engine start quickly, idle smoothly, pull strongly through the rev range, and use less fuel. Worn or fouled plugs make the engine feel a bit lazy and can nudge fuel consumption up.

Service guidance: most 2010 Impreza petrol models specify long‑life iridium plugs. Replacement timing varies by engine and usage, but a practical window is about 60,000–100,000 km for everyday driving, with turbo models typically on the shorter side. The exact interval and plug type should be confirmed in the vehicle’s maintenance booklet or parts label, ANZ catalogues list equivalent iridium options for EJ engines and a typical gap around 1.1 mm. Always replace all four plugs together.

Tips for the job: tackle it with a cold engine, blow any grit out of the plug wells, and use a quality 14 mm spark plug socket with a wobble extension. Access on the boxer can be snug, removing the air box on one side can help. Don’t use anti‑seize on new iridium plugs unless the plug maker explicitly says so, and torque them correctly—Subaru and plug makers specify a light crush on the washer, a typical spec for M14 taper/washer plugs in alloy heads sits around 18–25 Nm. Check coil boots and leads (where fitted) for cracking before refitting.

• Signs it’s time: rough idle or misfire under load
• Heavier fuel use and lazier acceleration
• Hard starting or a flashing check‑engine light

Done on time with the right iridium plugs and gap, the 2010 Impreza’s ignition stays crisp, fuel use stays sensible, and the flat‑four keeps its trademark smoothness. Sources referenced: Subaru Impreza MY2010 Owner’s Manual and Warranty & Maintenance Booklet, Subaru EJ-series service manual ignition section, NGK and Denso ANZ application catalogues for 2010 Impreza plug specifications.

Popular questions about 2010 Subaru Impreza spark plugs

What spark plugs does a 2010 Subaru Impreza use?
Most petrol models specify long‑life iridium plugs matched to the EJ engine’s heat range, with a typical gap near 1.1 mm. Exact part numbers vary by engine code (NA vs WRX turbo), so it’s best to cross‑check the owner’s manual or a reputable ANZ parts catalogue. Always fit a matched set of four plugs from a recognised brand.

How often should the plugs be changed?
For everyday use, expect 60,000–100,000 km on iridium plugs, with turbo models usually at the shorter end. If the engine is tuned, driven short trips, or shows misfire symptoms, inspect earlier. Follow the maintenance booklet for the official interval on the specific trim.

Can a DIYer change the plugs on a boxer engine?
Yes, with patience and the right tools. Access is tight on a flat‑four, so a wobble extension helps and removing the air box can create space. Work on a cold engine, keep debris out of the cylinders, torque to spec, and don’t over‑gap fine‑wire iridium electrodes.