Reviewed: 7 Best Spark Plugs For Subaru Forester

As a longtime Subaru owner, I know that reaching those notoriously tight spark plugs on the Boxer engine can be a pain, so when I do a plug change, I want to make sure I’m installing the absolute best spark plugs for subaru forester to maximize performance and longevity. Over the years, I’ve found that the right iridium or platinum plug can drastically improve cold starts, maintain strong fuel efficiency, and keep the ignition system running smoothly for 80,000 miles or more. This guide breaks down the top options for various Forester generations, ensuring you spend your time wrenching only once.

IMAGE	PRODUCT NAME	AMAZON LINK
	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
	A-Premium Iridium Platinum Spark Plugs Compatible with…	View on Amazon
	A-Premium Set of 4 Ignition Coil Pack and Iridium Spark…	View on Amazon
	4 pc DENSO Platinum TT Spark Plugs compatible with Subaru…	View on Amazon
	A-Premium Iridium Platinum Spark Plugs Compatible with…	View on Amazon
	Genuine OEM Subaru Spark Plugs Forester Impreza Legacy…	View on Amazon

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

If your Forester is a classic (1999–2004), sticking with genuine OEM parts is usually the safest bet for guaranteed fit and function, and this NGK kit delivers exactly that. These plugs are engineered specifically by Subaru’s factory supplier to meet the exact resistance and heat range requirements of the older SOHC non-turbo engines. You get reliability and consistency without the guesswork of aftermarket alternatives.

Key features that stand out:

• Genuine OEM Quality: These are the standard plugs originally installed on many pre-2005 Subaru models.
• Wide Non-Turbo Fitment: Excellent for older models like 1999-2004 Forester and Impreza non-turbo engines.
• Trusted Performance: Provides consistent ignition and reliable cold starts for aging engines.

Pros:
– Guaranteed fitment and function for specific older generations.
– Made by NGK, Subaru’s factory-preferred supplier.
– Excellent baseline performance for non-modified engines.

Cons:
– Not designed for modern turbo or DOHC engines.

Best for: Owners of pre-2005 non-turbo Subaru Foresters prioritizing OEM reliability.

Expert Opinion: For older Subaru Boxer engines where consistent performance and reliability are key, using the genuine manufacturer-specified plug (which in this case is NGK) minimizes the risk of engine codes or misfires.

4 pc NGK Iridium IX Spark Plugs compatible with Subaru Forester 2.5L H4 2011-2018

NGK’s Iridium IX line is renowned for bridging the gap between factory quality and enhanced performance, making this set one of the best spark plugs for subaru forester models spanning 2011 through 2018. The fine Iridium tip ensures extremely sharp, focused sparks, which results in better combustion and often a smoother idle. If you’re looking for a serious upgrade in durability and responsiveness over standard copper plugs for your naturally aspirated engine, this is a top contender.

Key features that stand out:

• Iridium Construction: Provides exceptional durability and high resistance to wear and heat.
• Improved Ignitability: Fine wire center electrode enhances ignition efficiency.
• Modern Fitment: Specifically designed for the 2.5L H4 non-turbo engines in the 2011-2018 generation.

Pros:
– Known for improving throttle response and starting capabilities.
– Excellent longevity, typically lasting up to 80,000 miles.
– NGK is a preferred brand by many professional mechanics.

Cons:
– Higher upfront cost compared to basic platinum options.

Best for: 2011-2018 Forester owners (2.5L non-turbo) seeking enhanced performance and long service life.

Expert Opinion: The Iridium IX is a performance staple. While it’s slightly pricier, the enhanced resistance to fouling and the consistent, powerful spark delivery make it ideal for the demanding, high-heat environment of the horizontally opposed engine.

A-Premium Iridium Platinum Spark Plugs Compatible with Subaru Outback, Forester, Impreza, Legacy & Mercedes-Benz C230 & Mitsubishi Outlander, Lancer, Eclipse & Hyundai Genesis Coupe, Pack of 4

This A-Premium plug offers a hybrid Iridium/Platinum design engineered for outstanding longevity—up to 100,000 miles—making it a fantastic set for those who prefer extended maintenance intervals. It features a robust design that accommodates a wide range of older and mid-generation naturally aspirated Subaru models (2004-2013 Forester). Its dual-material construction balances ignition performance with extreme durability.

Key features that stand out:

• Dual Alloy Construction: Iridium center electrode and Platinum core material ensure maximum lifespan.
• Extended Interval: Recommended replacement mileage is 80,000 to 100,000 miles.
• Broad Application: Suitable for many 2.5L non-turbo Subaru models across a decade of production.

Pros:
– Excellent value proposition given the long service life.
– Engineered for maximum ignition performance across compatible engines.
– Highly resistant to corrosion and thermal shock.

Cons:
– Its broad fitment means performance may not be as fine-tuned as dedicated NGK/OEM options.

Best for: Budget-conscious Subaru owners (2004-2013) looking for extreme longevity and reliability.

Expert Opinion: When considering the complexity of changing Forester plugs, the 100,000-mile rating on this plug is highly appealing. This plug focuses heavily on durability, providing peace of mind between service intervals.

A-Premium Set of 4 Ignition Coil Pack and Iridium Spark Plugs Compatible with Subaru Forester 2011-2012 2.5L, Impreza 2012 2.0L

For owners of the 2011-2012 Forester (2.5L NA), this kit offers a complete ignition tune-up solution, bundling four iridium spark plugs with four corresponding coil packs. As coil packs begin to degrade around the 80k to 100k mile mark, replacing both plugs and coils simultaneously is often the most economical and effective solution to curing misfires and poor fuel economy. The included iridium plugs ensure stable performance and increased fuel efficiency.

Key features that stand out:

• All-in-One Kit: Includes four iridium spark plugs and four direct replacement ignition coil packs.
• Iridium Performance: Delivers stable idle speed and super performance with reduced emissions.
• Buy with Confidence: Backed by a one-year unlimited-mileage guarantee.

Pros:
– Excellent value for a comprehensive ignition system overhaul.
– Simplifies the tune-up process by providing all necessary components.
– Improves starting speed and stabilizes engine idle.

Cons:
– Fitment is extremely narrow (only 2011-2012 2.5L NA Forester).

Best for: Forester owners of the specified 2011-2012 years needing a full ignition system refresh.

Expert Opinion: For vehicles nearing 100,000 miles, the ignition coils are just as critical as the plugs. Choosing a kit like this that pairs both components is a smart preventative maintenance measure against future misfire codes.

4 pc DENSO Platinum TT Spark Plugs compatible with Subaru Forester 2.5L H4 2005-2010

DENSO is another key player in the OE world, and their Platinum TT (Twin Tip) plugs offer unique technology specifically for the mid-generation 2005–2010 Forester. The twin-tip design—a 1.1mm platinum center electrode coupled with a titanium-enhanced alloy ground electrode—is engineered to reduce spark quenching. This results in a larger, more powerful spark, leading to faster starts and potentially superior fuel economy compared to standard plugs.

Key features that stand out:

• Platinum TT Design: Twin-tip configuration maximizes spark energy and reduces quenching.
• Superior Fuel Economy: Engineered to improve combustion efficiency.
• Improved Durability: Titanium-enhanced alloy ground electrode extends plug life.

Pros:
– Delivers a notably powerful and consistent spark.
– Excellent choice for reliable daily driving performance.
– Genuine DENSO quality ensures proper fitment.

Cons:
– Not as long-lasting as dedicated Iridium plugs (but durable for platinum).

Best for: 2005-2010 Forester owners prioritizing strong, reliable ignition and improved efficiency.

Expert Opinion: The Platinum TT design is a notable innovation. By having a free-standing firing pad, the plug allows the flame kernel to develop faster, which is particularly beneficial for maximizing performance in slightly older engines.

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

This specific A-Premium offering targets a crucial market: the modern Forester 2.0L Turbocharged engines (2014-2018). Turbo engines run hotter and operate under higher cylinder pressures than their non-turbo counterparts, requiring a spark plug with a specific heat range and gap size. These Iridium Platinum plugs meet those stringent requirements, offering exceptional ignitability and longevity (80,000–100,000 miles) critical for performance engines.

Key features that stand out:

• Turbo Specific: Designed explicitly for the higher demands of the H4 2.0L Turbocharged engine.
• Precise Specifications: Exact gap, thread, and reach to match OE requirements for turbocharged vehicles.
• High Longevity: Iridium/Platinum construction withstands extreme operating conditions.

Pros:
– Essential plug choice for maintaining peak performance in turbo engines.
– Exceptional heat resistance and durability.
– Engineered for exceptional ignitability crucial for forced induction.

Cons:
– Highly specialized fitment; do not use in non-turbo models.

Best for: Owners of 2014-2018 Subaru Forester 2.0L TURBO models who need high-performance, durable plugs.

Expert Opinion: Never cheap out on plugs for a turbocharged engine. The heat range of this Iridium/Platinum plug is specifically tailored to prevent detonation and pre-ignition in the 2.0L FA20 engine, making it a critical choice for reliable power.

Genuine OEM Subaru Spark Plugs Forester Impreza Legacy Crosstrek 2011-2017 22401AA781 Set OF 4

If you own a relatively recent, naturally aspirated Forester (2011–2017) and simply want the exact plug that came from the factory, this genuine OEM set (part number 22401AA781) is the straightforward solution. Opting for the genuine article ensures you maintain your vehicle’s factory specifications for emissions, fuel economy, and engine performance without any risk of compatibility issues.

Key features that stand out:

• Direct Factory Replacement: Guaranteed to match the original equipment specifications.
• Reliable Compatibility: Perfect fit for 2.5 non-turbo models from 2011–2017.
• Quality Assurance: Subaru OEM parts undergo rigorous quality control.

Pros:
– Zero risk of fitment or performance issues.
– Ideal for maintaining warranty requirements.
– Reliable and consistent performance across the full service interval.

Cons:
– Does not offer the extended life or performance boost of some aftermarket Iridium plugs.

Best for: 2011-2017 non-turbo Forester owners who demand exact factory specifications and reliability.

Expert Opinion: When in doubt, especially concerning modern engine control systems, the OEM plug is always the safest path. These plugs are calibrated precisely for the FB25 engine, offering the best baseline performance and longevity.

Practical Comparison Insights

When reviewing the best spark plugs for subaru forester, the decision often comes down to engine type and plug material.

If you drive a Turbocharged (XT) Forester, you must select a plug specifically rated for forced induction, such as the A-Premium Iridium Platinum for the 2.0L turbo. These plugs have specific heat ranges required to prevent high-heat damage.

For Naturally Aspirated (NA) Foresters, you have more flexibility. The choice is primarily between Iridium and Platinum:

• Iridium Plugs (NGK Iridium IX or A-Premium Iridium/Platinum): These are the high-end choice. They provide the longest service life (up to 100,000 miles) and offer the best, most consistent spark over time. They are the top recommendation if you hate having to reach the plugs frequently.
• Platinum Plugs (DENSO Platinum TT or OEM options): These are excellent workhorses, often providing a great balance of performance and value. While still long-lasting, they are generally recommended for intervals closer to 60,000–80,000 miles.

If your Forester is showing signs of ignition system fatigue (misfires, hesitation), the A-Premium coil and plug kit provides exceptional value for a complete ignition refresh on compatible models.

Final Verdict: Choosing the Right Spark Plug

Selecting the best spark plugs for subaru forester depends entirely on your model year and engine type (NA vs. Turbo).

Best Overall Durability and Performance (2.5L NA Models):
The 4 pc NGK Iridium IX Spark Plugs compatible with Subaru Forester 2.5L H4 2011-2018 takes the crown. NGK’s Iridium IX plugs offer the gold standard in lifespan and consistent ignition quality, making them worth the slightly higher cost for most daily drivers.

Best for Factory Purity (Recent NA Models):
If you want guaranteed, no-fuss reliability, the Genuine OEM Subaru Spark Plugs Forester Impreza Legacy Crosstrek 2011-2017 is the definitive choice. You can’t go wrong with the parts engineered specifically for your engine.

Best for Turbocharged Models (2.0L XT):
The A-Premium Iridium Platinum Spark Plugs Compatible with Subaru Forester 2014-2018, WRX 2015-2020, 2.0L, Pack of 4 is highly recommended. For the high heat and pressure of the turbo engine, choosing a plug designed to meet those specific thermal requirements is non-negotiable for engine health.

Best Spark Plugs For Subaru Forester FAQ

Why are changing the spark plugs on a Subaru Forester (Boxer Engine) so difficult?

The horizontal design of the Subaru Boxer engine means the cylinder heads are located on the sides of the engine bay, close to the frame rails. This drastically limits the working space, particularly for the two rear plugs. It often requires specific, shorter tools and careful maneuvering, especially compared to vehicles with inline or V-configuration engines.

How often should I replace the spark plugs in my Subaru Forester?

The replacement interval depends heavily on the type of plug installed. Most modern OEM or high-quality Iridium plugs are rated for 60,000 to 100,000 miles. Older copper plugs or basic platinum plugs might require replacement closer to the 30,000–45,000-mile mark. Always check your owner’s manual or the plug manufacturer’s recommendation.

What are the symptoms of bad spark plugs in a Forester?

Common symptoms indicating you need new best spark plugs for subaru forester include: Engine misfires (a noticeable shake or stumble, especially under load), decreased fuel economy, difficulty starting (excessive cranking time), sluggish acceleration, or the illumination of the Check Engine Light (CEL) indicating a specific cylinder misfire code.

Should I use Iridium or Platinum spark plugs?

Iridium is the superior material. Iridium plugs have a smaller center electrode, which provides a stronger, more efficient spark, and they are significantly harder and more durable than platinum. While Iridium plugs are usually more expensive, they typically last much longer (up to 100,000 miles vs. 60,000–80,000 miles for platinum), offsetting the initial cost.

Do I need to gap aftermarket spark plugs for my Subaru Forester?

While premium iridium and platinum plugs often come pre-gapped from the factory, it is always a best practice to double-check the gap against your specific engine’s requirement (found in the owner’s manual). Handling and shipping can sometimes cause the gap to shift, and setting the wrong gap can lead to misfires. Use a wire-style gap tool for Iridium and Platinum plugs to avoid damaging the fine tip.

Is using OEM spark plugs always the best option for my Forester?

OEM plugs are guaranteed to work perfectly with your engine and are the safest choice for reliability. However, high-quality aftermarket plugs from brands like NGK, DENSO, or specialized Iridium/Platinum offerings can often provide superior longevity or, in some cases, slightly enhanced performance compared to the basic factory plug, especially if you drive a spirited or modified vehicle.