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If your 2014-2018 Subaru Forester is showing rough idle, reduced throttle response, or harder cold starts, the correct spark plugs can make a big difference. Replacing aging or inappropriate plugs restores consistent combustion, helps maintain fuel economy, and reduces the chance of engine misfires. This guide covers the top spark plug options suited to the Forester across the 2014 to 2018 model years, focusing on durability, ignition quality, and heat range compatibility.Below you will find our shortlisted picks with clear reasons for inclusion, followed by the buying factors you should weigh and practical advice on installation and diagnostics.
Looking for other parts? See all Subaru Forester parts & accessories.
Top Picks at a Glance
| Best Overall The best all-around choice for most situations | Sixity Auto NGK Laser Iridium Spark Plugs, 4-Pack |  |
| Best Quality Built to a higher standard if you want something more solid | Genuine Subaru Spark Plugs 22401AA781 — Set of 4 |  |
| Best Value The sweet spot between price and what you get | BDFHYK Iridium Spark Plugs Set of 4 (93482) Compatible with Subaru 2.0L/2.5L H4 |  |
| Best Budget The cheapest option that still gets the job done reliably | daydmaly Platinum Iridium Spark Plugs (4-pack) |  |
| Highest Rated A top-rated pick with lots of positive feedback | NGK Iridium IX Spark Plugs, 4-Pack |  |
| Most Popular A crowd favorite that many people choose with confidence | NGK Iridium IX Spark Plug LKAR7BIX-11S, 4 Pack |  |
1. Sixity Auto NGK Laser Iridium Spark Plugs, 4-Pack
| Compatible vehicles | Subaru Forester 2.0L 2014-2018 |
|---|---|
| Quantity | 4 pack |
| Center electrode material | Iridium |
| Ground electrode material | Platinum |
These NGK Laser Iridium spark plugs are designed as direct replacements for the 2.0L Subaru Forester (2014–2018). They use a fine-wire iridium center electrode and a platinum ground electrode to improve ignitability and extend service life compared with standard copper plugs. Install them the same way as factory plugs; they are packaged as a four-pack so you can replace all cylinders at once. The iridium tip and copper core combination helps stable combustion, consistent starts and steady idling while also promoting efficient heat transfer under normal driving conditions. Because they are engineered for long life, you should be able to go much longer between changes versus basic replacements, which is convenient for everyday owners who want low-maintenance reliability. Expect typical limitations of high-performance precious-metal plugs such as a higher upfront cost than basic plugs and no performance gains beyond smoother ignition and longevity in stock engines.
Best for: Balanced owners who want reliable, low-maintenance ignition upgrades that prioritize longevity and smooth everyday driving for a 2014–2018 Subaru Forester 2.0L.
Less Ideal for: Drivers seeking measurable horsepower gains or racing-level performance should look at dedicated performance ignition parts instead.
- Fine-wire iridium center electrode for improved ignitability and longer life
- Platinum ground electrode and 98 percent copper core for efficient heat transfer
- Sold as a 4-pack for full-engine replacement in one service
- Engineered to match application-specific electrode configurations for consistent performance
- Higher upfront cost compared with basic copper replacement plugs
Verdict: Choose these iridium plugs if you want a durable, factory-quality ignition replacement that delivers reliable starts and long service intervals for a 2014–2018 Forester 2.0L.
2. Genuine Subaru Spark Plugs 22401AA781 — Set of 4
| Manufacturer | SUBARU |
|---|---|
| Brand | GENUINE SUBARU |
| Manufacturer Part Number | SUBARU22401AA781 |
These are genuine Subaru spark plugs (part 22401AA781) sold as a set of four for non-turbo EJ20B and EJ25B engines. They are used as direct factory-replacement plugs during routine tuneups to restore original ignition performance and smooth idle. Installation is straightforward because they match factory reach and heat range, so no gap changes are usually required. As OEM parts they offer consistent fitment and materials comparable to what the engine was designed for, which helps maintain factory drivability and throttle response. The practical benefits are reliability and parts-level compatibility with valve covers and ignition coil boots. Downsides for the performance-minded are limited: these are not marketed as high-performance or iridium-upgrade plugs, so they will not provide measurable gains in power or longevity over upgraded aftermarket iridium or platinum plugs. If you want factory-correct replacement that preserves stock behavior, these are a solid choice.
Best for: Owners who prioritize maintaining factory drivability and reliable, OEM-correct ignition performance during routine maintenance on non-turbo Subaru engines.
Less Ideal for: Drivers seeking maximum ignition longevity or measurable power gains should consider aftermarket iridium or performance spark plugs instead.
- Exact factory replacement fit for specified Subaru non-turbo engines
- Sold as a matched set of four for a complete tuneup
- Consistent factory-quality materials and construction
- Simple installation with factory reach and heat range
- Not a performance or long-life iridium/platinum upgrade
Verdict: Choose these OEM Subaru plugs if you want reliable, factory-correct replacements that preserve stock performance on non-turbo Forester engines.
3. BDFHYK Iridium Spark Plugs Set of 4 (93482) Compatible with Subaru 2.0L/2.5L H4
| Unit Count | 4 Count |
|---|---|
| Core Material | Iridium |
| Automotive Fit Type | Vehicle Specific Fit |
| Thread Size | RM |
These BDFHYK iridium spark plugs are a direct-fit replacement designed for Subaru 2.0L and 2.5L H4 engines listed by the manufacturer, providing the finer iridium center electrode and high-density ceramic insulator typical of long-life plugs. They are used the same way as factory plugs: remove old plugs, install the set of four with correct gap and torque, and expect improved ignition consistency and longer service intervals compared with standard copper plugs. Notable features include iridium electrodes for stronger, more reliable sparks and packaging intended as a vehicle-specific fit. In practical use you can expect steady cold starts, smoother idle, and modest fuel-effectiveness gains when worn plugs are replaced. Limitations are typical for aftermarket parts: fitment confirmation is needed against your exact model year and OEM part number, and performance gains are incremental rather than dramatic over recent factory iridium plugs. Installation is straightforward for anyone comfortable with basic maintenance, but professional installation eliminates risk of cross-threading or incorrect torque.
Best for: Drivers looking for a cost-effective, longer-lasting replacement spark plug to restore smooth starts and steady idling on Subaru 2.0L or 2.5L H4 engines who prefer pragmatic upgrades over performance-only parts.
Less Ideal for: People seeking race-level ignition components or large performance gains beyond stock tuning should consider high-performance branded alternatives designed for modified engines.
- Iridium center electrode for long service life and consistent ignition
- High-density ceramic insulator for good heat control and durability
- Sold as a set of four for full-bank replacement
- Vehicle-specific fit listing simplifies matching to Subaru H4 engines
- Aftermarket fit requires double-checking OEM part number and year fitment
Verdict: A practical, longer-life iridium replacement set that restores reliable ignition on Subaru 2.0L and 2.5L H4 engines without unnecessary complexity.
4. daydmaly Platinum Iridium Spark Plugs (4-pack)
| Included Components | 4 x Platinum Iridium Spark Plug |
|---|---|
| Core Material | Iridium |
| Automotive Fit Type | Universal Fit |
| Manufacturer Warranty Description | 90 days |
These daydmaly spark plugs pair an iridium central electrode with a platinum construction to offer a longer-life replacement for Subaru 2.0L and 2.5L H4 engines. They are supplied as a set of four and are intended for plug change service on 2013–2018 model-year Subaru vehicles listed by the manufacturer. In real-world use the fine iridium tip improves ignition consistency and can reduce misfires and rough idle compared with basic copper plugs, while the ceramic insulator and strengthened construction aim to resist fouling and heat-related wear. Installation is the same as standard spark plug replacement and fits typical DIY or shop service intervals. Limitations include that the listing is labeled universal fit so buyers should verify exact fitment and gap for their engine before installation, and the product comes from a third-party brand with a short 90-day warranty rather than a long OEM-backed guarantee.
Best for: Drivers seeking a budget-friendly, longer-life replacement spark plug set for routine maintenance on mid-2010s Subaru 2.0L or 2.5L H4 engines and who are comfortable verifying fitment and gap before installation.
Less Ideal for: Those who want an exact factory-brand replacement or an extended warranty and prefer parts with direct manufacturer fit confirmation without additional verification.
- Iridium center electrode for improved ignition reliability and longer service life
- Supplied as a full four-pack for a complete cylinder set replacement
- Ceramic insulator designed for high density and good electrical insulation
- Compatible with Subaru 2.0L and 2.5L H4 engines in the listed model years when properly verified
- Listed as universal fit so engine-specific gap and thread details must be checked before installing
- Short 90-day manufacturer warranty compared with longer-term options
Verdict: A cost-conscious way to upgrade to iridium-tipped plugs for mid-2010s Subaru H4 engines when you verify fitment and gaps before installation.
5. NGK Iridium IX Spark Plugs, 4-Pack
| Compatible engine | 2.5L H4 |
|---|---|
| Quantity | 4 pack |
| Center electrode | Iridium 0.6 mm tip |
| Core | 98 percent copper core |
These NGK Iridium IX spark plugs are a direct-replacement set intended to restore or maintain reliable ignition in the 2.5L Subaru Forester. They use a fine 0.6 mm iridium center electrode and tapered ground electrode to improve ignitability and provide a stable spark, which helps with throttle response and smoother acceleration during everyday driving. Construction that includes a high-conductivity copper core supports consistent heat transfer and predictable operating temperature, contributing to longer service life versus conventional plugs. Installation is the same as factory-style plugs, so a routine plug change at recommended intervals is straightforward for a technician or experienced DIYer. The main limitation is that these are a replacement designed for longevity and drivability rather than race use, so they are not optimized for high-RPM or heavily modified engines. Expect improved consistency and reduced replacement frequency compared with basic plugs, making them a solid reliability upgrade for stock Foresters.
Best for: Buyers who prioritize dependable, longer-lasting ignition for daily driving and want a factory-style replacement to maintain consistent engine performance.
Less Ideal for: Drivers running heavily modified engines or seeking spark plugs tuned for racing and extreme high-RPM performance should consider performance-specific options instead.
- Iridium 0.6 mm fine tip improves ignitability and throttle response
- Copper core promotes efficient heat transfer for stable operating temperature
- Pack of four covers a full 4-cylinder engine change
- Designed as a direct replacement for stock fitment in compatible Forester models
- Built for longevity and driveability rather than high-RPM or motorsport use
Verdict: Choose these NGK Iridium IX plugs when you want a durable, factory-style replacement that improves ignition consistency and reduces how often you need to change plugs on a stock Forester.
6. NGK Iridium IX Spark Plug LKAR7BIX-11S, 4 Pack
| Core Material | Iridium |
|---|---|
| Thread Size | M14 x 1.25 |
| Vehicle Service Type | Car, Truck |
| Position | Front, Rear |
NGK Iridium IX spark plugs are designed to deliver reliable ignition performance for drivers who want sharper throttle response and longer service life than standard plugs. The fine 0.6 mm iridium tip and tapered ground electrode produce a consistent, powerful spark that improves cold starts and throttle feel, while the longer insulator nose and corrugated ribs reduce fouling and flashover in everyday driving. These plugs include trivalent plating to resist corrosion and eliminate the need for anti-seize on the threads, and the triple gasket seal helps prevent combustion gas leakage. In practical use they are a direct, vehicle-specific replacement intended for performance-oriented street engines and are commonly chosen during routine tune-ups or when upgrading from basic plugs. Expect higher durability but also a higher upfront cost compared with plain nickel plugs, and installation still requires correct torque to protect cylinder head threads. For a Forester from the 2014 to 2018 range they provide a straightforward way to improve responsiveness without major modification.
Best for: Drivers who prioritize proven, performance-oriented ignition improvements and want a spark plug with wide user endorsement and long-term durability for routine maintenance or mild upgrades.
Less Ideal for: If you are strictly budget-constrained or replacing plugs on a seldom-driven utility vehicle, a lower-cost nickel plug is a simpler choice.
- Fine 0.6 mm iridium tip for stronger, more consistent spark and improved ignitability
- Longer insulator nose and corrugated ribs reduce fouling and flashover in normal driving
- Trivalent plating prevents corrosion and removes need for anti-seize on threads
- Vehicle-specific fitment and factory-quality engineering for reliable replacement
- Higher upfront cost than standard nickel plugs
Verdict: Choose these NGK Iridium IX plugs for a reliable, proven upgrade that sharpens throttle response and reduces fouling for 2014–2018 Forester drivers seeking long-lasting ignition performance.
Choosing the Right 2014-2018 Subaru Forester Spark Plug: Key Factors to Consider
Electrode Material and Longevity
Electrode composition largely determines service life and performance. Iridium and platinum alloys offer much longer life and more consistent spark performance than standard copper-core plugs. For the Forester, longer-life electrodes reduce the frequency of replacements, which matters if you drive in mixed urban and highway conditions.
Higher-end metals also allow for finer center electrodes, which concentrate spark energy and can improve combustion consistency and throttle response. Consider how often you want to replace plugs and whether you prioritize long-term reliability over the lower upfront cost of copper plugs.
Correct Heat Range
Heat range controls how quickly a plug sheds combustion heat. A plug that runs too hot can cause pre-ignition, while one that is too cold may foul from carbon buildup. For the 2014-2018 Forester engines, choose a heat range that suits your typical driving: shorter, low-load city trips tend to favor a slightly hotter plug to avoid fouling, while sustained highway driving can tolerate a colder-running design.
Matching heat range helps preserve electrode life and prevents misfire or knock issues. If you tow, carry heavy loads, or frequently drive at sustained high speeds, prioritize a heat range that resists overheating under load.
Gap Stability and Tolerance
Spark plug gap affects voltage requirement and combustion quality. A gap that widens or degrades with wear raises ignition voltage needs and can trigger misfires. Plugs with strong gap retention, often those with hardened or fine-wire electrodes, maintain performance over many heat cycles.
When replacing plugs, check and set the gap within the Forester's specification. If you drive in cold climates where battery output and starter performance are taxed, gap stability becomes more critical to avoid cold-start misfires.
Compatibility with Coil Boots and Reach
The physical design—thread reach and seat type—must match the Forester's cylinder head and ignition coil boots. A plug with incorrect reach can alter combustion characteristics or cause mechanical interference with the coil assembly. Similarly, some plugs require specific boot clearances or have taller insulators that affect fitment.
Confirm the plug thread length and seating style before buying. Proper fit prevents cross-threading, ensures correct heat transfer to the head, and allows secure torqueing to spec, all of which influence long-term reliability.
Resistance and Radio-Frequency Interference
Many modern plugs include a resistor to suppress radio-frequency interference with onboard electronics and sensors. For the Forester, maintaining low electromagnetic interference is important because it reduces the chance of sensor errors that could affect engine management and diagnostics.
If you operate aftermarket electronics or sensitive diagnostic tools, prefer plugs with suitable RFI suppression characteristics. Note that resistor plugs should still provide consistent spark energy; confirm that the chosen design balances suppression and ignition strength.
Durability Against Fouling and Corrosion
Plugs can degrade due to fouling from oil consumption, fuel additives, or carbon buildup, and threads can corrode in moist climates. Choose plugs with anti-corrosion coatings on the threads and insulators that resist glaze and deposits.
Durable designs reduce the risk of seized plugs and make future maintenance easier. If you frequently drive in wet or salty environments, prioritize corrosion-resistant finishes and robust insulator materials to extend service life.
Symptoms That Indicate Spark Plug Service Is Needed
Recognizing the signs of a failing spark plug helps you avoid drivability problems and potential engine damage. Common symptoms on a 2014-2018 Forester include rough idling, hesitation during acceleration, a noticeable drop in fuel economy, and intermittent misfires under load.
Cold-start issues are also a frequent indicator. If the engine struggles to fire cleanly when temperatures are low, or you notice a rough first few seconds after starting, worn or inappropriate plugs are a likely cause. Pay attention to the check engine light and stored misfire codes during diagnostics.
- Rough idle or vibration at idle
- Intermittent or consistent misfire codes
- Poor throttle response or hesitation
- Reduced fuel efficiency
- Hard starting in cold weather
Routine Maintenance Intervals and When to Replace
Recommended replacement intervals vary by electrode material and driving conditions. Iridium and platinum plugs commonly last longer than standard copper-core types. For typical mixed driving, expect long-life plugs to approach or exceed the manufacturer interval, while copper plugs may require more frequent attention.
If you notice any of the symptoms listed earlier, perform a visual inspection and gap check before assuming the full service interval. Replace plugs earlier if you frequently operate in short-trip urban driving, use ethanol-blended fuels heavily, or experience oil consumption that could foul electrodes.
- Inspect plugs during routine tune-ups or when diagnosing drivability issues
- Replace earlier if you see heavy carbon deposits or electrode wear
- Use long-life plugs to reduce frequency of service for high-mileage owners
Basic Diagnostic Checks Before Replacing
Before swapping plugs, rule out coil or ignition wiring issues that can mimic plug failure. A visual exam of plugs removed from the engine provides clues: light tan deposits indicate healthy combustion, while heavy black soot suggests fouling and oil-wetted electrodes suggest an oil control issue.
Measure the plug gap and inspect electrode wear patterns. If multiple cylinders show similar wear, the plugs themselves are likely at end of life. If only one cylinder is affected, look for coil or injector problems before changing all plugs.
- Check for consistent electrode coloration across cylinders
- Scan for misfire trouble codes to localize faulty cylinders
- Measure gap and note any irregular wear or deposit patterns
Installation Tips to Avoid Common Problems
When installing new plugs on the Forester, always clean the plug wells and use the correct torque to avoid over-tightening or under-tightening. Apply a light anti-seize only if the plug manufacturer recommends it, and avoid excess paste on the threads which can alter torque readings.
Ensure the gap is set to the vehicle specification prior to installation, and use a torque wrench to the correct spec to protect the cylinder head threads. Reinstall ignition coils carefully to avoid pinching boots and confirm electrical connectors are secure.
- Verify thread reach and seating type before installation
- Set the plug gap to Forester specification
- Torque plugs with a calibrated wrench and follow recommended sequence
Effects of Fuel Type and Driving Habits
Fuel composition and driving patterns affect how quickly plugs foul. Regular short trips and stop-and-go commuting promote carbon buildup, while occasional high-speed runs can help burn deposits off. Ethanol-blended fuels can accelerate deposits in some conditions, making gap retention and electrode durability more important.
If you use higher-octane fuel for specific driving needs, that does not change the plug heat range dramatically, but it can reduce knocking tendencies. Prioritize plug durability if your driving includes many short trips or if you live in an area with frequent cold starts.
- Short trips increase fouling risk and favor hotter plugs
- Highway driving can permit colder heat ranges that last longer
- Fuel additives and ethanol blends can influence deposit formation
When to Consult a Technician
If you observe persistent misfires after installing new plugs, or if a single cylinder repeatedly shows trouble, consult a technician. Persistent problems may indicate coil pack failure, injector issues, compression loss, or other mechanical faults beyond plug replacement.
Also seek professional help if you are unsure about torque specs, thread repair, or if a plug has broken during removal. Proper diagnosis prevents unnecessary part replacements and ensures long-term engine health.
- Persistent misfires after plug change
- Broken or seized plug during removal
- Uncertain torque or thread damage
Still looking for the perfect fit?
Select your Subaru Forester configuration to see the most relevant Spark Plugs recommendations
How We Chose the Best 2014-2018 Subaru Forester Spark Plug
We shortlisted spark plugs for the 2014-2018 Subaru Forester by applying criteria that reflect real-world driving and Subaru engine characteristics. Primary evaluation factors included electrode material and expected service life, ignition performance under varied temperatures, correct heat range for Forester engines, and gap stability after heat cycling. We also looked at compatibility with direct-reach and resistor-type requirements typical to these engines, as well as corrosion and thread-coating features that affect long-term serviceability.Additional filters removed options that require injector or ignition coil changes to function or that deviate from the Forester's recommended plug reach and torque specifications. We excluded tuning-only variants that sacrifice drivability for peak power and any plug designs known to be prone to fouling on typical Subaru engine oil consumption patterns. The final list favors plugs that balance long life, reliable cold-start performance, and consistent spark energy across normal driving conditions.
Our full evaluation process is outlined in our review methodology.
FAQ
How often should I change spark plugs on a 2014-2018 Subaru Forester?
It depends on the electrode material and driving conditions. Long-life iridium or platinum plugs can often approach the manufacturer's recommended interval, while copper-core plugs require more frequent replacement, especially with frequent short trips.
Can worn spark plugs cause a cold-start misfire in my Forester?
Yes. Worn or fouled plugs raise ignition voltage requirements and can cause misfires, particularly during cold starts when battery output and starter performance are lower.
Should I change the spark plug gap when replacing plugs in my Forester?
Always verify and set the gap to the vehicle specification before installation. Some long-life plugs are pre-gapped, but you should still confirm tolerance to ensure consistent ignition performance.
Are iridium plugs better than platinum for the Forester?
Iridium typically offers longer life and finer electrodes that can improve ignition consistency. However, the right choice depends on your priorities: longevity and reduced service frequency versus slightly lower initial cost for platinum.
Will a misfire always show a check engine light?
Not always immediately. Some intermittent misfires may not trigger a persistent check engine light but can still cause uneven running or reduced fuel economy. Scanning for stored or pending misfire codes helps identify intermittent issues.
Can I install spark plugs myself on a Forester?
Many owners can perform a plug change with basic tools and a torque wrench, provided they follow gap specs and torque values. Seek professional help if you encounter seized plugs, damaged threads, or recurrent misfires after installation.
Final Verdict
Prioritize plugs that match the Forester's heat range and physical fitment while balancing electrode material for your service preferences. Long-life iridium or platinum designs reduce maintenance frequency and often deliver more consistent cold-start behavior, while copper options may be appropriate if you plan regular interval maintenance.Weigh the tradeoffs between longevity, gap stability, and heat range for your typical driving. Choose plugs that align with how you drive and the climate you encounter to get the most reliable ignition performance from your 2014-2018 Subaru Forester.
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