Every 2015-2021 WRX left the factory with the same spark plug: the NGK Laser Iridium ILKAR8H6, sold under NGK part number 96024. Whether you’re running a bone stock WRX or a built one pushing well past factory power, having the right plug (and the right gap) in the FA20DIT matters for reliable ignition. The NGK ILKAR8H6 linked below is all most WRX owners will ever need. Own a 2002-2014 WRX or a 2002-2021 STI instead? Those run the EJ20/EJ25, not the FA20DIT — see our WRX & STI spark plug guide for the right part number.
WRX FA20DIT Spark Plugs
The NGK ILKAR8H6 is the stock heat range plug for every 2015-2021 WRX, and it’s the same plug Subaru specs for the 2014-2018 Forester XT since both share the FA20DIT engine. NGK’s own spec sheet lists it at heat range 8 with a 0.024″ factory gap (NGK, ILKAR8H6 / 96024 product page). It’ll comfortably handle a stock car all the way up to a solid Stage 2 build, roughly 300 whp.
Once a build starts pushing past that, it’s time to step up to a colder plug. We recommend the NGK R2558E-9, one heat range colder than stock, for anything in the 350-600whp range. More boost means more heat in the combustion chamber, and the colder plug pulls that heat out faster so you don’t end up chasing a heat-soak misfire.
One thing worth double-checking before you buy: FA20 and FA20DIT are not the same engine. The naturally-aspirated FA20 runs in the BRZ, FR-S, and 86. The turbocharged, direct-injected FA20DIT is what’s actually in a WRX. If a listing just says “FA20 spark plug” without specifying DIT, don’t assume it’s the same part until you’ve matched it against ILKAR8H6.
It’s a mix-up we see often in build mod lists, too: a “one step colder” note that’s actually just describing NGK 96024 by its part number, which is the stock heat range plug, not a colder one. Worth remembering whenever you’re reading someone else’s mod list: check the actual part number, not just how it’s labeled.
FA20DIT Spark Plug Gap & Torque Specs
- Factory gap: 0.020″-0.022″
- Torque: 10.8-14.5 lb-ft on an aluminum head, per NGK’s own torque spec for this plug — though most WRX engine bays don’t leave enough clearance to get a torque wrench on the plug. Snug against the crush washer, by feel, is how most owners actually do this job.
One catch: the ILKAR8H6 ships from NGK pre-gapped to 0.024″, wider than Subaru’s factory spec, so plan on adjusting it down before it goes in. Use a wire-type gap tool rather than a flat feeler gauge. The iridium center electrode on this plug is thin and can bend or chip if you’re not careful with it.
When to Replace WRX Spark Plugs
Plan on new plugs around 30,000 miles, sooner if you notice any of the usual warning signs: power loss, a misfire, a rougher idle than normal, a slower crank on startup, or worse fuel economy than you’re used to. On a direct-injection engine like the FA20DIT, carbon buildup on the intake valves tends to show up on a similar timeline and shares some of the same symptoms, so it’s worth a look at the same time.
Why We Only Sell Genuine NGK Plugs
Counterfeit NGK spark plugs are a real problem, not a scare story. NGK’s own anti-counterfeiting page warns buyers to be wary of unusually low prices on e-commerce sites and to buy only through authorized distribution channels (NGK, “Counterfeit Spark Plugs: The Ignition Villains That Could Ruin Your Engine”). Fakes typically swap the iridium center electrode for a standard nickel one machined down to look similar, and NGK has documented cases of counterfeit plugs melting at the tip and damaging the engine around them.
Amazon and eBay listings for NGK plugs are exactly the kind of unverified, third-party channel that warning is about — you’re often buying from whoever’s currently winning the buy box, not NGK or an authorized reseller. Every plug ffrides sells, including both the ILKAR8H6 and R2558E-9 above, comes through NGK’s authorized distribution channel.
Frequently Asked Questions
What spark plug does a 2015-2021 WRX use stock?
The NGK Laser Iridium ILKAR8H6, sold under NGK part number 96024, at heat range 8. It’s shared with the 2014-2018 Forester XT, which runs the same FA20DIT engine.
What gap should WRX spark plugs be set to?
0.020″-0.022″, per Subaru’s factory spec. NGK ships the ILKAR8H6 pre-gapped wider, at 0.024″, so it needs adjusting down at install with a wire-type gap tool.
Do I need colder spark plugs for a Stage 2 WRX?
Not automatically. Stock heat range covers up to roughly 300 whp. Past that, step up to the one-step-colder NGK R2558E-9.
How often should WRX spark plugs be replaced?
Around 30,000 miles, or sooner if you notice power loss, misfire, rough idle, slow starts, or reduced fuel economy.
Shop both plugs directly: NGK ILKAR8H6 (stock) for stock-to-mild builds, or NGK R2558E-9 (one step colder) once you’re past roughly 300 whp.