2022 Subaru Outback Spark Plug Type & Gap

Quick reference

Engine	OEM Plug PN	Aftermarket (NGK/Denso/Motorcraft)	Gap (in/mm)	Torque (lb-ft / Nm)	Interval(miles/km)
2.5L H4 (FB25DI)	NGK SILZKAR7B11	NGK SILZKAR7B11 (stock)	0.044 / 1.1	15.2 / 20.6	60,000 / 96,000
2.4L H4 Turbo (FA24F)	NGK SILZNAR6C7Y	NGK SILZNAR6C7Y (stock)	0.024-0.028 / 0.6-0.7	15.2 / 20.6	60,000 / 96,000

Why the right plug matters

Choosing the correct spark plug for your 2022 Subaru Outback is critical for optimal engine performance, fuel efficiency, and longevity. The "right" plug isn't just about fitment; it's about heat range, electrode material, and proper gapping.

Heat Range

The heat range of a spark plug refers to its ability to dissipate heat from the combustion chamber. A "hot" plug retains more heat, while a "cold" plug dissipates it more quickly. Using a plug with an incorrect heat range can lead to problems. A plug that's too hot can cause pre-ignition (where the fuel ignites before the spark event), leading to engine knock and potential damage. A plug that's too cold can foul easily with carbon deposits, leading to misfires and poor performance.

Electrode Metal: Iridium vs. Platinum vs. Copper

Modern engines like those in your 2022 Subaru Outback typically use long-life spark plugs made with exotic materials like iridium or platinum.

• Iridium plugs (like those specified for the Outback) are the most advanced, offering superior durability and a finer electrode tip for a more focused spark. This leads to better fuel efficiency and smoother operation. They generally have a lifespan of 60,000 to 100,000 miles.
• Platinum plugs are a step up from copper, offering good durability and performance. They are often found in older vehicles or as an upgrade to copper plugs. Their lifespan is typically around 40,000 to 60,000 miles.
• Copper plugs have a copper core electrode, which is an excellent conductor of electricity. However, copper is a soft metal, so these plugs wear out relatively quickly, with a lifespan of around 15,000 to 20,000 miles. They are primarily used in older, less demanding applications.

For your 2022 Subaru Outback, both engine options specify iridium spark plugs from the factory, designed for longevity and optimal performance.

How to gap a spark plug

Spark plug gapping is the process of precisely setting the distance between the center and ground electrodes. While many modern iridium plugs come pre-gapped, it's always a good idea to check them before installation. Incorrect gapping can lead to misfires, reduced fuel economy, and even engine damage.

Tools You'll Need:

• Wire or Ramp-Style Gap Gauge: These are inexpensive tools specifically designed for measuring spark plug gaps. Avoid using coin-style gauges on fine-wire iridium plugs, as they can damage the delicate electrode.

Steps:

1. Consult the Specs: Refer to the "Quick Reference" table above for the correct gap specification for your 2022 Outback's engine.
2. Measure the Gap: Gently slide the appropriate wire gauge or ramp gauge between the electrodes. There should be a slight drag.
3. Adjust (if necessary):
   • To increase the gap: Carefully bend the ground electrode slightly outward using the gapping tool. Be very gentle, as the ground electrode can break if bent too far.
   • To decrease the gap: Gently tap the ground electrode on a clean, hard surface. Re-measure and repeat until the correct gap is achieved.

Crucial tip: Never pry or force anything against the center electrode, especially on iridium plugs. The fine tip is extremely fragile and can be easily damaged, rendering the plug useless.

Replacement procedure tips

Replacing spark plugs on a 2022 Subaru Outback, while a DIY-friendly task for some, does require proper technique due to the Boxer engine design and the coil-on-plug ignition system.

Coil-on-Plug (COP) Removal

Your Outback uses a coil-on-plug ignition system, meaning each spark plug has its own ignition coil directly mounted on top. To access the spark plugs:

1. Disconnect the Battery: Always disconnect the negative battery terminal before working on any electrical components.
2. Remove Engine Covers: Depending on your model, you may need to remove plastic engine covers to gain access.
3. Disconnect Electrical Connector: Carefully press the release tab on the coil pack's electrical connector and pull to disconnect it.
4. Remove Coil Pack Bolts: Use the appropriate socket to remove the bolt(s) securing the coil pack to the valve cover.
5. Remove Coil Pack: Gently twist and pull the coil pack straight up to remove it from the spark plug well. Avoid yanking, as this can damage the coil boot.

Anti-Seize Debate

There's ongoing debate about whether to use anti-seize compound on spark plug threads. Spark plug manufacturers (like NGK) generally advise against it for plugs with a special coating on the threads, as it can alter torque readings and lead to over-tightening. If the plugs you're installing have a shiny, metallic coating on the threads, they likely do not require anti-seize.

However, if you're using plugs without this coating or if you're in a corrosive environment, a tiny amount of anti-seize applied sparingly to the threads (avoiding the electrodes) can prevent seizing.

Dielectric Grease on Boots

Applying a small amount of dielectric grease inside the spark plug boot (the rubber end that connects to the spark plug) is highly recommended. Dielectric grease acts as an insulator, preventing voltage leaks and ensuring a good electrical connection. It also helps lubricate the boot, making future removal easier and preventing the boot from sticking to the porcelain insulator of the spark plug.

Torque Specifications

Always tighten spark plugs to the manufacturer's specified torque. Over-tightening can strip the threads in the cylinder head or crack the spark plug's ceramic insulator. Under-tightening can lead to looseness, allowing combustion gases to escape and potentially damaging the cylinder head. Refer to the "Quick reference" table for the correct torque specifications for your 2022 Outback.

Known Issues

Fortunately, the 2022 Subaru Outback, with its FB25DI and FA24F Boxer engines, does not have any widespread, commonly known spark plug-related issues akin to the notorious Ford 3-valve 2-piece spark plug breakage or GM 5.3 ionization-sensing coil problems. Subaru engines are generally well-regarded for their reliability when properly maintained.

The most common "issues" are usually related to incorrect spark plug installation (e.g., cross-threading, incorrect torque, dropping a plug, or damaging the electrode during gapping), using the wrong spark plug type, or neglecting replacement intervals. Stick to the OEM-specified plugs and follow proper installation procedures, and your Outback's ignition system should serve you well.

Need plugs replaced? Find a shop on Repairius.