2023 Subaru Outback Spark Plug Specifications

Quick reference

Why the right plug matters

Choosing the correct spark plug is crucial for engine health, performance, and fuel economy. The key factors are heat range and electrode material.

• Heat Range: This determines how quickly the plug dissipates heat from the combustion chamber. A plug that is too "hot" (slow heat dissipation) can lead to pre-ignition, while a plug that is too "cold" (fast heat dissipation) can foul quickly. Both the FB25D and FA24F engines are designed for a specific heat range, and deviation is not recommended.
• Electrode Material: Modern engines like those in the 2023 Outback use iridium-tipped spark plugs from the factory. These are long-life plugs, vastly superior to the older copper or platinum plugs. Iridium is an extremely hard and dense precious metal, which allows for a very fine center electrode. This fine wire design lowers the voltage required to create a spark, resulting in a more consistent and powerful spark, improved throttle response, and better fuel efficiency. While cheaper copper plugs exist, they have a much shorter lifespan (20,000-30,000 miles) and are not recommended for this vehicle.

How to gap a spark plug

Proper spark plug gap is critical. Even brand-new plugs should be checked before installation. Use a wire-style or feeler gauge tool to measure the distance between the center and ground electrodes. If adjustment is needed, gently bend the ground electrode. Never pry against the center electrode, as this can damage the fragile iridium tip.

Replacement procedure tips

The 2023 Outback, like most modern vehicles, uses a coil-on-plug ignition system. This means each spark plug has its own ignition coil mounted directly on top of it, eliminating the need for a distributor and spark plug wires.

• Coil-on-plug removal: Each coil is held down by a single bolt. After removing the bolt, gently twist and pull the coil straight up to remove it.
• Anti-seize debate: Subaru does not recommend using anti-seize compound on the spark plug threads. The OEM NGK plugs have a special plating that provides the necessary anti-seize properties. Applying additional compound can lead to over-torquing, which can damage the threads in the aluminum cylinder head or even break the spark plug.
• Dielectric grease: Apply a small amount of dielectric grease to the inside of the coil boot before reinstalling it. This helps seal out moisture and makes future removal easier.

Known issues

Fortunately, the engines in the 2023 Subaru Outback do not have any widespread known issues related to spark plug design or failure, such as the infamous Ford 3-valve two-piece plug breakage or GM 5.3L engine ionization-sensing coil problems. Following the recommended service intervals and using the correct OEM-spec plugs will ensure a long and trouble-free life for your ignition system.

Need plugs replaced? Find a shop on Repairius.