Subaru Forester Spark Plugs: Intervals, Fitment & Warning Signs
On the Forester, misting water over a suspected coil genuinely helps confirm it as the cause of a misfire — plus a warning about counterfeit NGK plugs.
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Subaru Forester Spark Plugs: OEM Part Number
Subaru Forester Spark Plugs: A Cheap Part That Causes Expensive-Feeling Problems
A worn set of spark plugs in the Subaru Forester doesn't make itself obvious: idle roughens slightly, acceleration loses a bit of urgency, and both symptoms are easy to blame on something else entirely. Given how inexpensive the part is, it often gets neglected for far longer than it should.
Subaru Forester Spark Plugs: What They Do
Every combustion cycle in the Subaru Forester's petrol engine starts with a spark plug igniting the compressed fuel-air mixture, and their condition shapes efficiency, economy and smoothness directly. Diesel versions don't need them at all, relying purely on compression to ignite fuel.
Subaru Forester 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 |
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A Genuinely Useful, Real Diagnostic Technique Worth Trying — Subaru Forester 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 Forester 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.