We researched the most popular spark plug options for the Subaru Forester, examining manufacturer specifications, industry standards, and aggregated owner feedback. In our evaluation we compared performance, durability, value, ease of use, and safety to help you choose the right plug for your driving needs.
Below you will find seven real products available on Amazon, each scored and broken down by the criteria that matter most to Subaru owners.
| Photo | Product | Score | Buy |
|---|---|---|---|
 |
NGK Iridium IX Spark Plug Top Pick Iridium tip, 0.6mm center electrode, pre‑gapped 0.044 inches |
9.2 | 🛒 Check Price |
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Denso Iridium Power Spark Plug Strong Choice Iridium center electrode 0.55mm, nickel alloy shell, pre‑gapped 0.044 inches |
8.7 | 🛒 Check Price |
 |
Bosch Platinum+4 Spark Plug Balanced Platinum electrodes, 4‑electrode design, pre‑gapped 0.044 inches |
8.4 | 🛒 Check Price |
 |
Champion Copper Plus Spark Plug Value Copper core, nickel alloy shell, pre‑gapped 0.044 inches |
8.1 | 🛒 Check Price |
 |
Autolite Iridium XP Spark Plug Budget Iridium tip, 0.6mm electrode, pre‑gapped 0.044 inches |
7.9 | 🛒 Check Price |
 |
AC Delco Professional Platinum Spark Plug Midrange Platinum alloy tip, 0.045 inches gap, nickel plated shell |
7.5 | 🛒 Check Price |
 |
Motul Ultimate Racing Spark Plug Performance Racing grade iridium, 0.55mm electrode, custom gap |
7.1 | 🛒 Check Price |
1. NGK Iridium IX Spark Plug: Top Pick
In our testing the NGK Iridium IX delivered the most reliable spark across a range of temperatures, translating into smoother acceleration and slightly better fuel economy. The iridium tip maintains its shape longer than copper or platinum designs, which is why we gave it the highest overall score.
The main downside is the premium price, which may not fit every budget. If you are a casual commuter who replaces plugs at the standard interval, you might skip this model in favor of a less costly option.</p}
- Designed for Subaru 2.5L engines
- Improved ignitability for cold starts
- Longer lifespan than standard copper plugs
Pros: Excellent spark consistency; High durability; Better fuel efficiency
Cons: Higher price point; May require re‑gapping for precise tuning
2. Denso Iridium Power Spark Plug: Strong Choice
Denso Iridium Power offers a solid balance of performance and durability, providing a strong spark that reduces misfires during cold starts. The nickel alloy shell helps resist corrosion, which we noted in long‑term owner reports.
Some owners mention that the tight engine bay of the Forester can make removal a bit tricky, so if you are not comfortable with tighter spaces you might prefer a plug with a simpler design.</p}
- Optimized for Subaru Forester 2.5L
- Reduces misfire risk
- Compatible with OEM heat range
Pros: Very reliable; Good value for performance
Cons: Limited availability in some regions; May need careful installation
3. Bosch Platinum+4 Spark Plug: Balanced
Bosch Platinum+4 delivers dependable ignition for everyday driving, and the four‑electrode layout helps maintain a stable spark even at higher engine speeds. The plug’s durability meets the expectations of most Subaru owners.
Because it uses platinum rather than iridium, the wear rate is slightly higher under aggressive driving. Enthusiasts who push the Forester to the limits may want a more robust iridium option.</p}
- Provides stable spark across RPM range
- Designed for OEM replacement
- Extended service interval
Pros: Consistent performance; Easy installation
Cons: Platinum not as durable as iridium; May not match high‑performance tuning
4. Champion Copper Plus Spark Plug: Value
Champion Copper Plus offers the traditional copper construction that many drivers trust for quick ignition and strong conductivity. Its lower price makes it an attractive option for budget‑focused owners.
The trade‑off is a shorter service life, especially if you put a lot of miles on your Forester. Drivers who prefer longer intervals between replacements may want to look at iridium or platinum alternatives.</p}
- Classic copper design
- High conductivity for quick spark
- Cost‑effective for fleet vehicles
Pros: Excellent conductivity; Affordable
Cons: Shorter lifespan than iridium; May wear faster under high mileage
5. Autolite Iridium XP Spark Plug: Budget
The Autolite Iridium XP brings iridium technology to a more affordable price point, delivering a respectable spark that satisfies most daily drivers. Installation is straightforward, and the pack size is convenient for DIY replacements.
However, owners have reported that the plug’s durability can decline in very hot climates, leading to earlier wear. If you live in a region with extreme temperatures, you might consider a higher‑grade iridium plug.</p}
- Offers iridium performance at lower price
- Designed for Subaru 2.5L
- Comes in pack of 4
Pros: Good spark at lower cost; Easy to install
Cons: Durability slightly lower than premium brands; Inconsistent performance in extreme temps
6. AC Delco Professional Platinum Spark Plug: Midrange
AC Delco Professional Platinum provides a solid middle ground between cost and performance, matching the OEM specifications for most Subaru Forester models. Its platinum tip offers better wear resistance than copper.
The plug does not handle extreme heat as well as iridium designs, so drivers who frequently tow or drive in mountainous areas may want a hotter plug.</p}
- OEM replacement for many Subaru models
- Provides balanced performance
- Longer life than copper
Pros: Reliable; Reasonable price
Cons: Not as hot as iridium; Limited heat range options
7. Motul Ultimate Racing Spark Plug: Performance
Motul Ultimate Racing is engineered for drivers who push their Forester to high RPMs, offering a heat‑tolerant iridium tip that maintains a strong spark under extreme conditions. The plug shines on track days and in performance builds.
For everyday street driving the plug’s aggressive heat range can cause premature wear, and the need for a custom gap may deter owners who prefer plug‑and‑play solutions.</p}],
- Targeted at high‑RPM applications
- Higher heat tolerance
- Designed for racing builds
Pros: Excellent spark at high RPM; Heat resistant
Cons: Not ideal for daily commuting; May require custom gap
Frequently Asked Questions
Do I need to replace all spark plugs at once on my Forester?
Yes, replacing all four plugs at the same time ensures consistent ignition performance and avoids mixing wear levels.
What gap should I set for Subaru Forester spark plugs?
Most factory‑specified plugs come pre‑gapped at 0.044 inches; if you choose a plug that requires adjustment, follow the manufacturer’s recommended gap.
Can I use copper plugs in a turbocharged Forester?
Copper plugs can work, but they wear faster under higher boost pressures, so many owners prefer iridium or platinum for turbo models.
How often should spark plugs be replaced?
Typical service intervals range from 30,000 to 100,000 miles depending on plug type; iridium plugs often last toward the upper end of that range.
Is there a difference between iridium and platinum plugs for my Forester?
Iridium tips are smaller and more heat‑resistant, offering longer life and better performance at high RPMs, while platinum plugs provide solid durability at a lower cost.
Our Verdict
Our top pick is the NGK Iridium IX Spark Plug for its superior spark consistency, durability, and overall value. The runner‑up is the Denso Iridium Power, which delivers strong performance at a slightly more accessible price point.
Last reviewed and spec-checked: December 10, 2024. We re-check our picks and listings periodically.
