Iridium Platinum Spark Plugs for Subaru Impreza WRX STi 2.5L EJ Turbo (Set of 4)

If you drive a Subaru Impreza WRX STi with the 2.5L EJ turbo engine, you've probably already learned that these boxer engines aren't shy about telling you when ignition components are past their prime — a little hesitation off boost, a rough idle, maybe a check engine light for a random misfire. This set of four Subaru WRX STI spark plugs is built with iridium platinum tips to give that EJ turbo a clean, consistent spark, and it's sized as a direct replacement so you're not guessing on fitment.

A Direct-Fit Spark Plug Set for the EJ Turbo

This is a 4-pack, matching the EJ 2.5L turbo's cylinder count, and the plugs cross-reference to OE/interchange numbers ILFR6B and SILFR6A, with manufacturer part number A0283A0010. If your Impreza WRX STi originally came with plugs under either of those interchange numbers, this set drops in without modification. It's an aftermarket replacement rather than a Subaru-branded part, but the thread reach, seat, and heat range are matched to factory spec so the swap is straightforward, not a project.

Why Iridium Platinum Instead of Standard Copper

Iridium platinum spark plugs earn their keep on turbocharged engines like the EJ 2.5L, where cylinder pressures and combustion heat run higher than anything a naturally aspirated engine sees. Iridium is a harder, more heat-resistant metal than the nickel alloy used in basic copper plugs, so the center electrode can be ground down to a much finer point. A finer point concentrates the spark, which generally supports more complete combustion and a steadier idle, and iridium plugs tend to hold their shape and resist electrode erosion longer than standard copper plugs under comparable conditions. That doesn't translate into a specific mileage number for your car — that depends on how it's driven, tuned, and maintained — but the material itself is a genuine upgrade over stock-grade copper for a boosted flat-four engine.

It's worth saying plainly what this upgrade isn't: it isn't a tune, and it won't change your power figures on its own. What it does is give the EJ's ignition system a more consistent spark across the RPM range, which matters more on a turbo engine than on a naturally aspirated one, since boost adds cylinder pressure that a tired plug has to work harder to fire through. Think of it as keeping the ignition side of the engine from being the weak link, not as a performance part in its own right.

Signs Your STi's Plugs Are Overdue

Most people don't replace spark plugs on a schedule — they replace them when something starts feeling off. On an EJ turbo, that usually shows up as a rough or uneven idle, a flat spot when you get into boost, worse fuel economy than you remember, or a check engine light throwing a random or cylinder-specific misfire code. Cold starts can get a little rougher too, since a worn plug has a harder time firing consistently before the engine's up to temperature. None of those symptoms are exclusive to bad plugs — coils and injectors can cause similar complaints — but plugs are the cheapest thing to rule out first, and on a turbocharged engine, a weak spark under load is exactly the kind of thing that gets worse before it gets better.

Subaru WRX STI Spark Plugs — Specifications

• Part type: Spark plug, sold as a set of 4
• Material: Iridium platinum tip
• Interchange / OE part numbers: ILFR6B, SILFR6A
• Manufacturer part number: A0283A0010
• Fitment: Direct replacement, aftermarket — Subaru Impreza WRX STi 2.5L EJ turbo engine
• Fuel type: Gasoline
• Manufacturer warranty: 1 year

Installation Notes

Swapping spark plugs on the EJ25 is a job most people comfortable with basic hand tools can handle in an afternoon — a spark plug socket, a torque wrench, and a dab of anti-seize on the threads are really all you need. Because the coil packs sit right on top of each plug, you'll spend more time moving intake components out of the way to reach the rear bank than you will actually swapping the plugs. Torque them to your factory service manual spec instead of just cranking them down by feel, since over-tightening an iridium plug can crack the shell or strip the head. If you want a general primer on how spark plugs work and why heat range and gap matter, the Wikipedia entry on spark plugs is a solid, neutral reference to skim before you start.

Confirm Your Fitment First

Subaru revised EJ engine details more than once across model years, so it's worth double-checking against your VIN or the numbers stamped on your old plugs before you order. If you're not sure whether ILFR6B or SILFR6A matches what's currently in your Impreza WRX STi, reach out through our contact page and we'll help confirm it before you buy. If you're after a plug that isn't listed anywhere on the site, our request a part page is the fastest way to get us looking for it on your behalf.

It's also worth noting that these are listed as a direct, aftermarket replacement rather than a Subaru dealer part, which is how we're able to offer a set of four iridium platinum plugs at this price. The physical fit, thread pitch, and heat range are matched to the OE numbers above, but if you're the type who only runs factory-branded ignition components, that's worth knowing going in.

Backed by a 1-Year Warranty

Every set of these Subaru WRX STI spark plugs ships with a 1-year manufacturer warranty, so if a plug fails outside of normal wear and tear, you're covered — the specifics of what's included are on our warranty page. Questions about processing time or where your order currently sits are answered on our shipping and track your order pages, and our FAQ covers most of the other questions we get about fitment and installation. If you're servicing other parts of the ignition or engine system while everything's apart, our engine parts collection has related components worth a look.

A tired set of spark plugs is one of those maintenance items that's easy to put off, mostly because the car still runs — right up until the misfire gets worse, fuel economy drops, and the check engine light won't clear. If your WRX STi's EJ turbo is due, this iridium platinum set is a straightforward way to get the ignition side back where it belongs, without paying dealer prices to do it.