2016 Subaru Outback Spark Plug Specs

Quick Reference

Why the right plug matters

Choosing the correct spark plug for your 2016 Subaru Outback is crucial for optimal engine performance, fuel efficiency, and longevity. Three key factors set spark plugs apart: heat range, electrode material, and gap.

Heat Range

Spark plugs are designed with a specific heat range, which refers to their ability to dissipate heat from the combustion chamber. A "hotter" plug retains more heat, while a "colder" plug dissipates it faster. Subaru engineers carefully select the appropriate heat range for each engine to prevent pre-ignition (pinging) and fouling. Using a plug with an incorrect heat range can lead to engine damage or reduced performance.

Electrode Metal (Iridium vs. Platinum vs. Copper)

Modern vehicles like the 2016 Subaru Outback typically come with long-life iridium or platinum spark plugs from the factory. These precious metals are excellent conductors and resist wear much better than traditional copper. This allows for smaller, finer electrodes that deliver a more consistent and powerful spark, leading to improved combustion and longer replacement intervals.

• Iridium: The most common choice for modern engines, iridium offers superior durability and conductivity, allowing for extremely fine electrodes and extended service life (often 60,000 miles or more).
• Platinum: Another durable option, platinum plugs also offer extended life compared to copper, though generally not as long as iridium. They are often found on vehicles specifying a 60,000-mile interval.
• Copper: While excellent conductors, copper electrodes wear relatively quickly, necessitating much shorter replacement intervals (typically 30,000 miles or less). You generally won't find copper plugs as OEM in a 2016 Outback.

For your 2016 Subaru Outback, both the 2.5L FB25 and 3.6L EZ36D engines come equipped with long-life iridium spark plugs from the factory, designed for a 60,000-mile replacement interval.

Spark Plug Gap

The gap between the center and ground electrodes is critical for a strong, consistent spark. Too small a gap can result in a weak spark and misfires, while too large a gap can overwork the ignition coils and also lead to misfires. The specified gap for both engines in your Outback is 0.044 inches (1.1 mm).

How to gap a spark plug

While most iridium and platinum plugs come pre-gapped, it's always a good practice to double-check the gap before installation, especially for traditional copper or platinum plugs. For iridium plugs, extreme care must be taken as the fine electrode can be easily damaged.

1. Obtain a gapping tool: A wire-type feeler gauge is recommended for accurately measuring the gap without damaging the delicate electrode tip. Avoid coin-style gapping tools on fine-wire plugs.
2. Measure the current gap: Carefully insert the appropriate wire gauge into the gap. It should slide in with slight resistance.
3. Adjust if necessary: If minor adjustment is needed, gently bend the ground electrode using the gapping tool's adjustment slot. Never pry against the center electrode.
4. Re-measure: Confirm the gap is correct before installation.

Replacement procedure tips

Replacing spark plugs on a Subaru Boxer engine can be a bit more challenging than on inline or V-configuration engines due to the horizontally opposed cylinder layout. Here are some tips:

• Access: Expect limited space, especially on the driver's side. You may need to remove air intake components or other accessories to gain better access to the coil-on-plug units.
• Cool-Down: Always ensure the engine is completely cool before starting the procedure. Removing plugs from a hot aluminum cylinder head can strip the threads.
• Coil-on-plug Removal: The 2016 Outback uses a coil-on-plug (COP) ignition system. Each spark plug has its own ignition coil directly above it. Carefully disconnect the electrical connector and then unbolt the coil (usually a 10mm bolt). Gently twist and pull to remove the coil from the spark plug well.
• Anti-seize Debate: While many technicians traditionally use a tiny amount of anti-seize on spark plug threads, Subaru (and NGK/Denso) generally recommend against it for modern nickel-plated spark plugs. The nickel plating provides adequate anti-seize properties, and adding more can affect torque readings, potentially leading to overtightening and thread damage. If you choose to use it, apply an extremely thin coat and reduce the torque specification by about 20%.
• Dielectric Grease: Apply a small dab of dielectric grease inside the boot of each coil-on-plug unit before reinstallation. This helps to seal out moisture, prevents corrosion, and makes future removal easier.
• Torque Wrench: Always use a torque wrench to tighten spark plugs to the manufacturer's specification (15.2 lb-ft or 20.6 Nm). Overtightening can strip cylinder head threads or damage the spark plug, while undertightening can cause misfires or allow the plug to loosen.

Known Issues

The 2016 Subaru Outback generally does not have widespread "known issues" specific to its spark plugs like the problematic two-piece plugs found in some Ford 3-valve engines or the ionization-sensing coils on certain GM 5.3L engines. However, like any vehicle, misfires can occur due to:

• Worn or fouled spark plugs: Especially if the replacement interval is exceeded.
• Failing ignition coils: While designed to last, coils can fail over time, leading to misfires.
• Oil leaks into spark plug wells: Leaking valve cover gaskets can allow oil to pool around the spark plug, causing misfires and premature plug failure. Inspect the wells for oil when replacing plugs.

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