2024 Subaru Crosstrek Spark Plug Guide

Quick Reference

Why the right plug matters

Spark plugs are vital for your engine's performance, fuel economy, and emissions. Using the correct spark plug for your 2024 Subaru Crosstrek is not just a recommendation; it's crucial for maintaining optimal engine health. The "heat range" of a spark plug refers to its ability to dissipate heat. A plug that is too hot can cause pre-ignition and detonation, leading to engine damage. Conversely, a plug that is too cold can lead to fouling and misfires. Subaru engines, especially the FB series, are finely tuned and require a specific heat range.

The electrode material also plays a significant role. Most modern Subaru vehicles, including the 2024 Crosstrek, come equipped with iridium spark plugs from the factory. Iridium is an extremely durable and corrosion-resistant metal, allowing for a much finer electrode tip. This finer tip concentrates the spark, leading to a more efficient burn and extended service life (typically 60,000 miles or more). Platinum plugs offer a longer lifespan than traditional copper plugs but not quite as long as iridium. Copper plugs, while excellent conductors, have a shorter lifespan and are generally not recommended for modern engines designed for iridium or platinum.

How to gap a spark plug

Properly gapping a spark plug is critical for a strong, consistent spark. While most iridium plugs come pre-gapped, it's always a good idea to double-check, especially if you're using an aftermarket plug. For your 2024 Subaru Crosstrek, the recommended gap is 0.044 inches (1.1 mm).

To gap a spark plug, you'll need a wire-type spark plug gapping tool. Never use a flat, coin-style gapping tool on fine-wire iridium or platinum plugs, as this can damage the delicate electrode tip. Carefully slide the wire gauge of the correct thickness between the center electrode and the ground electrode. If the gap is too small, use the bending tool on the gauge to slightly pry the ground electrode open. If the gap is too large, gently tap the ground electrode on a clean, hard surface to close it. Always adjust the ground electrode only, never apply pressure to the center electrode.

Replacement procedure tips

Replacing spark plugs on a Subaru Boxer engine, particularly the FB series in the Crosstrek, can be a bit more involved due to the horizontally opposed cylinder layout. The spark plugs are located on the sides of the engine, which are tucked away.

1. Access: You'll need to remove the airbox on one side and possibly the battery and/or washer fluid reservoir on the other for easier access to the coil-on-plug units.
2. Coil-on-Plug Removal: The 2024 Crosstrek uses a coil-on-plug ignition system. Each spark plug has its own ignition coil directly mounted on top of it. Carefully disconnect the electrical connector from each coil, then unbolt the coil (usually a single bolt) and gently pull it straight up to remove it.
3. Spark Plug Removal: Use a dedicated spark plug socket (typically 14mm or 16mm, thin-walled) with an extension and a universal joint if needed. Loosen the plugs counter-clockwise. Take care not to drop anything into the spark plug wells.
4. Anti-Seize Debate: There is ongoing debate about using anti-seize on spark plug threads. Modern spark plugs often come with a special coating on the threads, and applying anti-seize can alter the torque readings, potentially leading to over-tightening and damage to the cylinder head threads. Subaru generally does not recommend anti-seize for their factory plugs. If you choose to use it, apply a very thin coat and reduce your torque specification by about 20-30%.
5. Dielectric Grease: It's good practice to apply a small amount of dielectric grease inside the spark plug boot (the part of the coil that connects to the spark plug). This helps prevent moisture entry and makes future removal easier.
6. Torque Specification: Tighten the new spark plugs to 15.0 lb-ft (20.0 Nm). Using a torque wrench is highly recommended to prevent over or under-tightening.

Known issues

The Subaru FB series engines (2.0L and 2.5L) in the 2024 Crosstrek are generally quite reliable in terms of spark plug-related issues. Unlike some other manufacturers that have experienced problems with multi-piece designs or specific coatings, Subaru's coil-on-plug system with iridium plugs has proven robust. There are no widespread "known issues" regarding spark plug breakage or premature failure unique to the 2024 Crosstrek. Regular maintenance and using the correct spark plugs are key to avoiding any potential problems.

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