Subaru Impreza Spark Plugs: Intervals, Fitment & Warning Signs
On the Impreza, misting water over a suspected coil genuinely helps confirm it as the cause of a misfire — plus a warning about counterfeit NGK plugs.
Illustration for editorial purposes
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OEM Part Number: confirm via engine code — aftermarket NGK 90935 / Bosch 0 242 135 517
| Petrol engines in this generation | 1.6i (GT2, GT3), 2.0i (GT6, GT7), 2.0 e-BOXER (GTE) |
|---|---|
| Spark plugs (aftermarket) | NGK stock no. 92217 (iridium, 0.8 mm gap, M12x1.25, 14 mm hex); NGK 90935 (iridium, 1.1 mm gap, M12x1.25, 14 mm hex); NGK 91899 (iridium, M12x1.25, 14 mm hex); Bosch 0 242 135 517 (0.7 mm gap, M12x1.25, 14 mm hex); Bosch 0 242 129 529 (1.1 mm gap, M12x1.25, 14 mm hex); Denso IXEH22TT (iridium centre, platinum earth, M12x1.25); Champion OE256 (iridium, 0.7 mm gap, 14 mm hex); Champion OE253 (iridium, 1.0 mm gap, 14 mm hex) |
| Genuine (OE) numbers quoted | 22401-00Q0K (Kamoka 7100015) |
| Fitment notes | The current Impreza takes a long-reach iridium M12x1.25 plug with a 14 mm hex; there are 0.7 mm and 1.1 mm gap versions, so confirm the engine before ordering. The M14x1.25 nickel plugs listed (for example NGK 6465, Denso K20TT) belong to older Imprezas. No change interval is quoted. |
Subaru Impreza Spark Plugs: A Cheap Part That Causes Expensive-Feeling Problems
The Subaru Impreza's spark plugs rarely fail dramatically; they just quietly degrade, showing up as a rougher idle or slightly blunted acceleration that gets blamed on other things. The part costs next to nothing, which paradoxically makes it one of the most commonly neglected items under the bonnet.
Subaru Impreza Spark Plugs: What They Do
On the Subaru Impreza, the compressed fuel-air mixture in each cylinder is ignited by the spark plugs, and their condition feeds directly into combustion efficiency, fuel economy and how smoothly the engine runs. Only petrol engines use them; diesels rely on compression alone.
Subaru Impreza Spark Plugs: Generations & Spark Plug Count
| Diesel variants, where fitted | Not applicable — diesel engines use compression ignition and have no spark plugs at all |
|---|---|
| Petrol variants (all trims, including WRX/STI) | 4 spark plugs — Subaru's distinctive flat-four "boxer" layout is still a four-cylinder engine for plug-count purposes, just with the cylinders arranged horizontally in opposing pairs rather than in a line or a V |
Subaru Impreza Spark Plugs: Watch: Replacing It
Same GT platform and FB20 engine as 2017- Impreza; generic FB20 option https://www.youtube.com/watch?v=X0gGmrNfI18
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A Genuinely Useful, Real Diagnostic Technique Worth Trying — Subaru Impreza Spark Plugs
If you suspect a specific ignition coil is causing a misfire, this is genuinely worth trying: lightly misting water over the suspected coil with the engine running and watching whether it immediately stumbles or misfires is a genuinely practical way to confirm the coil as the cause, since water finding its way into a coil with a cracked casing can cause the spark to short and jump elsewhere instead of reaching the cylinder.
It's also genuinely worth knowing an honest warning about parts sourcing: numerous documented reports describe counterfeit NGK spark plugs being sold through online stores, worth bearing in mind if a genuine-brand plug replacement doesn't resolve a misfire as expected.
Subaru Impreza Spark Plugs: Warning Signs, DIY Difficulty & Aftermarket Advice
These are the same regardless of make or model — see our full Spark Plugs Guide for symptoms of worn plugs, why matching your exact plug specification matters, and trusted brands to buy from.
More Subaru Spark Plugs
The same part, covered across other Subaru models.