2022 Subaru Forester Spark Plug Type, Gap & Torque Specs

Quick Reference

Why the Right Plug Matters

Your Subaru's engine is a finely tuned machine, and the spark plug is a critical component in the combustion process. It's not just about creating a spark; it's about delivering the right spark at the right time and in the right temperature range. Using the correct spark plug ensures optimal performance, fuel economy, and engine longevity.

• Heat Range: The "8" in the NGK part number (DILKAR7B8) denotes its heat range. This refers to the plug's ability to dissipate heat from the combustion chamber. A plug that is too "hot" (doesn't dissipate heat well enough) can lead to pre-ignition (detonation), which can cause severe engine damage. A plug that is too "cold" can accumulate carbon deposits, leading to misfires. The factory-specified heat range is engineered for the specific operating temperatures of your Forester's 2.5L direct-injection engine.

• Electrode Material: The OEM plugs for your Forester are Iridium-tipped. Compared to older copper or even platinum plugs, iridium offers significantly better durability and performance. Its extremely high melting point allows for a very fine center electrode, which requires less voltage to create a spark. This results in a more consistent and stable spark, improving throttle response and fuel efficiency. While they have a higher upfront cost, their long service life (60,000 miles in this case) makes them a sound investment compared to copper plugs that might need changing every 20,000-30,000 miles.

How to Gap a Spark Plug

Properly gapping a spark plug is crucial for a healthy ignition system. The gap is the distance between the center electrode and the ground electrode. If the gap is too small, the spark may be weak. If it's too large, it may fail to fire at all, causing a misfire.

Most modern iridium plugs, like the NGK DILKAR7B8 specified for your Forester, come pre-gapped from the factory. It is always a best practice to verify the gap before installation, but you must be extremely careful. The fine-wire iridium center electrode is very brittle and can be easily damaged.

1. Use the Right Tool: Use a wire-style or feeler gauge tool. Avoid the common "coin-style" gappers, as they can put pressure on the fragile center electrode and snap it off.
2. Check the Gap: Gently slide the 0.032" (0.8mm) wire of your gauge between the electrodes. It should have a slight drag. If it doesn't fit or is too loose, an adjustment is needed.
3. Adjust Carefully: To adjust, only bend the ground strap (the L-shaped electrode). Never pry against or touch the center electrode. Use a dedicated spark plug gapping tool that hooks the ground strap to gently bend it in small increments until the correct gap is achieved.

Replacement Procedure Tips

The 2022 Forester uses a modern coil-on-plug ignition system, which simplifies the replacement process compared to older distributor-based systems. Here are some tips for a smooth job:

• Coil-on-Plug Removal: Each spark plug has its own ignition coil sitting directly on top. To access the plug, you must first remove the single bolt (typically 10mm) holding the coil in place. Gently twist and pull the coil straight up and off the spark plug. The rubber boot can sometimes create a seal, requiring a firm but steady pull.
• The Anti-Seize Debate: The question of whether to use anti-seize compound on spark plug threads is a hot topic. NGK, the OEM supplier, officially recommends against using it on their modern plugs. The threads on these plugs have a special trivalent plating that acts as its own anti-seize and corrosion inhibitor. Applying additional anti-seize can act as a lubricant, leading you to inadvertently over-torque the spark plug. Over-torquing can stretch the plug's metal shell, leading to heat transfer issues or, in the worst case, a broken plug in the cylinder head, resulting in a very expensive repair. Always follow the dry torque specification.
• Dielectric Grease: While anti-seize on the threads is not recommended, applying a small amount of dielectric grease to the inside of the ignition coil boot is a great practice. This grease is a non-conductor that helps seal out moisture, prevents corrosion on the terminals, and makes it easier to remove the coils in the future. Do not apply it to the spark plug terminal itself, just the boot.

Known Issues

Thankfully, the FB25D engine in the 2022 Forester does not have any widespread, well-documented issues related to spark plug failure, such as the infamous breakage problems seen on some older Ford 3-valve Triton engines. The single-piece design of the NGK plugs is robust and reliable when installed correctly.

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