Best Spark Plugs For Subaru WRX

If you drive a Subaru WRX, especially if you’re running a modified engine or just hitting high mileage, you know how crucial the right plugs are for performance. I’ve spent time under the hood of several WRXs—from the newer FA20 (2.0L) to the classic EJ (2.5L) models—and selecting the best spark plugs for Subaru WRX is key to maintaining consistent boost, smooth idle, and avoiding knock. This guide cuts through the noise, comparing the top seven tested iridium and platinum options to ensure your Boxer engine runs exactly as it should.

IMAGE	PRODUCT NAME	AMAZON LINK
	4 pc NGK Laser Iridium Spark Plugs compatible with Subaru…	View on Amazon
	A-Premium Iridium Platinum Spark Plugs Compatible with…	View on Amazon
	NGK 96024 ILKAR8H6 Iridium Spark Plug, Pack of 4	View on Amazon
	Genuine Subaru Iridium Spark Plugs 22401AA670 / SILFR6A for…	View on Amazon
	4 pc NGK Laser Iridium Spark Plugs compatible with Subaru…	View on Amazon
	OEM Genuine NGK Spark Plugs Kit for Subaru Impreza…	View on Amazon
	4 pc NGK Iridium IX Spark Plugs compatible with Subaru…	View on Amazon

4 pc NGK Laser Iridium Spark Plugs compatible with Subaru WRX 2.0L H4 2015-2020

If you own a modern WRX with the FA20 engine and want the reliability and longevity that NGK is known for, these Laser Iridium plugs are an excellent choice. They are specifically designed for the high-heat and high-pressure environment of a turbocharged engine, providing improved efficiency and reducing the chance of misfires under heavy boost. These are often considered the gold standard for maintaining OE performance levels over long replacement intervals. Their dual-electrode design ensures the spark gap stays accurate for far longer than traditional plugs.

Key features that stand out:
Improved Combustion: – Advanced center and ground electrodes produce complete and efficient combustion.
Reduced Misfires and Emissions: – Promotes sharper spark focus for fewer misfires, boosting performance and fuel economy.
Corrosion Resistance: – Durable shell ensures long-lasting sparking capabilities even in harsh conditions.
NGK Reliability: – Built by the world leader in spark plug design, ensuring OEM-level quality.

Pros:
– Exceptional longevity (up to 100k miles).
– Optimized for the modern WRX FA20 DIT engine.
– Reliable ignition consistency under boost.
– Direct-fit OEM replacement quality.

Cons:
– Higher upfront cost compared to standard copper plugs.

Best for: Stock or lightly modified 2015-2020 WRX owners focused on maximum durability and OE performance.

Expert Opinion: NGK’s Laser Iridium series is generally the most recommended plug for daily-driven turbocharged cars requiring maximum service life. They are crucial for maintaining the precise timing required by the FA20 engine management system.

A-Premium Iridium Platinum Spark Plugs Compatible with Subaru Forester 2014-2018, WRX 2015-2020, 2.0L, Pack of 4

This A-Premium set offers a robust Iridium Platinum combination, designed to match the performance specifications of the OE plugs for the FA20 WRX platform (2015-2020). By combining a Platinum core with an Iridium tip, these plugs are engineered to maximize ignition performance while ensuring a very long lifespan. They boast an impressive 80,000 to 100,000-mile replacement recommendation, making them a fantastic budget-friendly alternative to pure NGK. They provide strong, focused ignition energy required for turbocharged applications.

Key features that stand out:
Dual Material Construction: – Iridium tip for superior spark and Platinum core for excellent heat dissipation.
OE Specifications: – Features the correct 5000 ohms resistance and 0.024-inch gap size for direct WRX fitment.
Exceptional Ignitability: – Designed alongside OEM standards to ensure optimal performance.
High Longevity: – Engineered for performance intervals between 80,000 and 100,000 miles.

Pros:
– Great value proposition for Iridium/Platinum quality.
– Long recommended service interval.
– Direct replacement for the WRX 2.0L Turbo engine.
– Strong focus on maximum ignition performance.

Cons:
– An aftermarket brand, which some enthusiasts avoid when mapping modified engines.

Best for: Budget-conscious WRX 2.0L owners seeking high quality and excellent service life.

Expert Opinion: For non-track use and standard mileage intervals, this combination of Iridium and Platinum offers a highly reliable spark. Always confirm the exact gap before installation, especially with high-boost engines.

NGK 96024 ILKAR8H6 Iridium Spark Plug, Pack of 4

The NGK 96024, or ILKAR8H6, is recognized globally as the specific original equipment replacement spark plug for many modern Subaru turbocharged applications. When you buy this specific part number, you are getting the exact quality, reliability, and durability you would expect from the manufacturer that supplies Subaru directly. Choosing this specific OEM part number eliminates guesswork, guaranteeing proper fitment and heat range for optimal engine health, especially under warranty.

Key features that stand out:
True OEM Standard: – Often specified as original equipment for reliability and durability.
Proven Quality: – NGK is the world’s largest supplier of OEM spark plugs, guaranteeing consistency.
Precise Fitment: – Engineered specifically to match the required resistance and heat range of compatible engines.
Performance and Longevity: – Provides the best combination of reliable performance and long lifespan.

Pros:
– Guaranteed OEM quality and fitment.
– Extremely high reliability.
– Excellent resistance to fouling and pre-ignition.
– Ideal for maintaining factory specifications.

Cons:
– Can sometimes be slightly harder to source than generic options.

Best for: FA20 WRX owners who prioritize using the exact OE manufacturer part for maintenance or warranty adherence.

Expert Opinion: If your car is stock and you want to ensure zero deviations from the factory setup, the specific OE part number like the 96024 is the safest and most reliable route.

Genuine Subaru Iridium Spark Plugs 22401AA670 / SILFR6A for WRX & STi Legacy Forester Outback Impreza OEM Set of 4

For owners of the previous generation WRX/STI running the venerable 2.5L Turbo EJ engine, these Genuine Subaru plugs are the direct OEM replacement. This set is branded by Subaru but manufactured by NGK (using the SILFR6A code), giving you the ultimate confidence in fitment and quality. These plugs are designed specifically to handle the demands of the 2.5L turbocharged platform (including many STI models) and are the recommended choice when servicing these classic performance engines.

Key features that stand out:
Genuine Subaru Part: – Guaranteed fitment and quality, eliminating uncertainty.
NGK Manufacture: – Manufactured by NGK (SILFR6A), combining brand quality with OEM approval.
EJ Engine Specific: – Designed for the 2.5L Turbo engines found in various WRX and STI models (2012-2016 WRX listed).
Iridium Construction: – Ensures excellent conductivity and long-term durability.

Pros:
– The absolute best choice for true OEM replacement on 2.5L Turbo engines.
– Reduces the risk of incorrect heat range or gapping issues.
– NGK Laser Iridium resistor technology utilized.
– High durability and long service life.

Cons:
– Compatibility is limited strictly to the 2.5L Turbo engines mentioned.

Best for: Owners of 2.5L Turbo WRX/STI models (EJ platform) seeking guaranteed Genuine Subaru parts.

Expert Opinion: Using true Genuine Subaru parts, even if manufactured by NGK, provides peace of mind. For high-mileage or modified EJ engines, we often recommend checking the gap and potentially tightening it slightly, depending on the tune.

4 pc NGK Laser Iridium Spark Plugs compatible with Subaru WRX STI 2.5L H4 2013-2018

This is another specialized NGK Laser Iridium option, but specifically tailored for the high-performance STI 2.5L H4 engine from 2013 to 2018. For STI owners who demand the highest level of proven durability and consistent performance, these are hard to beat. Laser Iridium construction provides superior resistance to fouling and wear, which is critical in the heavily boosted EJ25 engines. They are a direct replacement, ensuring ease of installation and guaranteed vehicle compatibility.

Key features that stand out:
STI Specific Application: – Verified fitment for the WRX STI 2.5L H4 engine models (2013-2018).
Genuine NGK Quality: – Includes original packaging and hardware for assurance.
Laser Iridium: – Known for exceptional longevity and stability in extreme operating temperatures.
Direct Replacement: – Simplifies the installation process without requiring modifications.

Pros:
– Highly durable and long-lasting plug.
– Proven performance in high-boost STI applications.
– Excellent resistance to electrode degradation.
– Genuine NGK components.

Cons:
– Not suitable for the newer 2.0L WRX (FA20) engine.

Best for: WRX STI owners seeking a long-life plug capable of handling the demands of the EJ25 motor.

Expert Opinion: Laser Iridium is the top-tier NGK option for durability. While some tuned STI owners might opt for the Iridium IX (reviewed below) for marginally better ignition performance, the longevity of the Laser is unmatched for daily driving.

OEM Genuine NGK Spark Plugs Kit for Subaru Impreza Outback Legacy Baja Forester SET OF 4

While not strictly for the turbocharged WRX, this kit provides insight into the NGK relationship with naturally aspirated (Non-Turbo) Subaru engines, which some earlier WRX/Impreza models share heritage with. This kit is important for owners servicing older 1990s and early 2000s Subarus (Legacy, Impreza, Forester) with the SOHC non-turbo engines. These are standard copper or platinum plugs designed for reliability and extended service life in lower-power, less heat-intensive applications. It’s a reliable maintenance item for a diverse range of older Subarus.

Key features that stand out:
Broad Subaru Fitment: – Covers a large range of older 1.8L, 2.2L, and 2.5L SOHC Non-Turbo engines.
Genuine OEM Part Number: – Uses Subaru part number 22401AA310, ensuring original fit.
Reliable Construction: – Designed for dependable starts and smooth operation in older platforms.
Kit of Four: – Conveniently packaged for a complete replacement.

Pros:
– Perfect fit for older, naturally aspirated Subaru models.
– Excellent maintenance item for fleet or historical vehicles.
– Affordable and dependable genuine OEM quality.

Cons:
– Completely unsuitable for any modern or turbocharged WRX/STI engine.

Best for: Owners performing maintenance on older, non-turbo Subaru models outside the WRX/STI performance bracket.

Expert Opinion: For the specific applications listed, these are the correct plugs. However, it is vital that WRX owners understand these plugs have the wrong heat range and design for forced induction and should only use Iridium or Platinum options rated for turbocharging.

4 pc NGK Iridium IX Spark Plugs compatible with Subaru WRX STI 2.5L H4 2013-2018

The NGK Iridium IX plugs are the choice of many enthusiasts looking for a performance edge, especially those running slightly higher-than-stock boost levels on their STI. These plugs feature an extremely fine Iridium tip electrode, which maximizes ignitability and provides a very consistent spark, crucial for preventing high-load knock. While they do not offer the same longevity as the Laser Iridium, the Iridium IX is favored for its enhanced sparking performance and stability under aggressive tuning. They are considered a minor upgrade over the standard OE Laser Iidium plugs for performance applications.

Key features that stand out:
Performance Focused: – Fine wire Iridium center electrode maximizes spark efficiency and ignitability.
High Heat Range Stability: – Excellent thermal dissipation, crucial for high-boost applications.
Anti-Fouling: – Tapered ground electrode minimizes quenching and prevents carbon buildup.
Direct STI Fitment: – Verified compatibility with the WRX STI 2.5L H4 2013-2018 models.

Pros:
– Superior ignitability compared to dual-tip designs.
– Excellent choice for moderately tuned STI engines.
– Strong resistance to thermal shock.
– Proven performance in competitive driving environments.

Cons:
– Service life is typically shorter (around 30k-40k miles) compared to Laser Iridium (80k-100k miles).

Best for: Enthusiasts with tuned WRX STI (EJ25) engines who prioritize maximum spark performance over long replacement intervals.

Expert Opinion: When running a highly aggressive tune or track driving the STI, the Iridium IX is the go-to plug, often paired with a slightly tighter gap to hold the spark under immense pressure.

Helpful Comparison Insights

Choosing the best spark plugs for Subaru WRX heavily depends on whether you drive a newer 2.0L (FA20) or an older 2.5L (EJ25).

For the FA20 (2.0L WRX 2015+): Your engine requires a specific heat range and resistance. Options like the NGK Laser Iridium 96024 are almost mandatory for reliable, long-term performance because they match the factory specifications perfectly. The A-Premium plugs offer a solid alternative if you’re looking to save money while maintaining high longevity.

For the EJ25 (2.5L WRX/STI): You have two excellent NGK paths. If you want maximum longevity and factory reliability, the 4 pc NGK Laser Iridium compatible with STI 2.5L is the way to go. However, if your car is tuned, the NGK Iridium IX offers a slight edge in ignitability, which can be critical for fighting knock at high boost, but be ready to replace them more often. Genuine Subaru parts are also available for those who want the true OEM stamp of quality on their EJ motor.

Material Matters: If your priority is service life (80k+ miles), stick with Laser Iridium or Iridium/Platinum dual-tipped plugs. If your priority is maximum spark focus and performance, the Iridium IX is superior, though it sacrifices long-term durability. Never use standard copper plugs in a modern turbocharged WRX as they will lead to rapid fouling and potential engine issues due to the heat range mismatch.

Final Verdict

Making the right choice for your WRX is all about balancing performance needs with expected service life.

The Best Overall Plug for Daily Driving WRX (2.0L FA20): We recommend the NGK 96024 ILKAR8H6 Iridium Spark Plug. It is the true OEM replacement, providing unmatched reliability, exceptional longevity, and guaranteed compatibility with the high-tech FA20 engine management system.

The Performance Choice for Tuned STI (2.5L EJ25): For enthusiasts running custom tunes and high boost, the 4 pc NGK Iridium IX Spark Plugs compatible with Subaru WRX STI 2.5L is the winner. They offer the necessary sharp, consistent spark that heavily modified engines demand, provided you are willing to check and replace them every 30,000–40,000 miles.

The Safest Bet for EJ Platform Longevity: If you have an STI and you’re primarily driving stock or lightly modified, the 4 pc NGK Laser Iridium compatible with Subaru WRX STI 2.5L is the better investment due to its vastly superior lifespan.

Frequently Asked Questions About the Best Spark Plugs for Subaru WRX

Q1: Do I need to gap my new Iridium spark plugs for my WRX?

A: Even if the plugs are “pre-gapped,” it is highly recommended to always check the gap before installing them in your WRX, especially if the car is tuned. For stock FA20 (2.0L) engines, the gap is typically tight (around 0.024 inches). If you are running high boost or a custom tune on an EJ25, tuners often recommend tightening the gap slightly (e.g., down to 0.026–0.028 inches) to help prevent spark blow-out under peak cylinder pressure.

Q2: How often should I replace the spark plugs in my turbocharged WRX?

A: The recommended replacement interval varies by plug type. Laser Iridium and Iridium/Platinum plugs are rated for longevity, typically lasting 60,000 to 100,000 miles in stock applications. However, if you use Iridium IX or are running a heavily tuned engine, we advise shortening the interval to 30,000–40,000 miles. Frequent checks are essential to prevent misfires and maintain WRX performance.

Q3: What is the difference between Laser Iridium and Iridium IX?

A: NGK Laser Iridium plugs are designed primarily for longevity. They often use a platinum tip on the ground electrode alongside the Iridium center electrode to minimize gap wear over a very long time. Iridium IX plugs are designed for performance; they use a thinner Iridium tip for maximum sparking focus and better ignitability, but they wear out faster because they lack the platinum reinforcement on the ground electrode.

Q4: Can using the wrong heat range plug cause knock in my WRX?

A: Yes, absolutely. Using a spark plug that is too “hot” (meaning it retains heat longer) can cause the tip to overheat, leading to pre-ignition or severe detonation (knock) in a high-boost WRX engine. Conversely, a plug that is too “cold” can lead to excessive fouling. Always use the specific heat range recommended by Subaru or your tuner, particularly for the turbocharged FA20 and EJ25 platforms.

Q5: Are generic aftermarket plugs safe for a high-performance WRX engine?

A: While some aftermarket brands offer high-quality alternatives (like the A-Premium option reviewed), many WRX owners prefer NGK or Genuine Subaru due to the precision required by the ECU. Incorrect resistance or heat ranges from lesser-known brands can introduce problems like miscommunication with the coil packs or unstable ignition timing, risking engine damage, especially during high-speed boost.

Q6: What does the “LKAR8H6” code mean on the NGK plugs?

A: The alphanumeric code on NGK plugs is critical. It describes the thread size, construction, resistance, and most importantly, the heat range. For modern WRXs, the “8” in the ILKAR8H6 refers to a relatively cold heat range, which is necessary to dissipate the extreme heat generated by the turbocharged engine. Always ensure your replacement spark plug uses the correct number for the heat range.