2015 Honda Accord: Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2015 Honda Accord is crucial for optimal engine performance, fuel efficiency, and emissions. There are several factors that make a "right plug" – most notably, the heat range and the electrode material.

Heat Range

The heat range refers to a spark plug's ability to dissipate heat from the combustion chamber. A plug that is too "cold" (dissipates heat too quickly) can lead to carbon fouling, misfires, and poor fuel economy. A plug that is too "hot" (dissipates heat too slowly) can cause pre-ignition (pinging or knocking) and detonation, potentially damaging engine components. Honda engineers meticulously select the ideal heat range for your Accord's engine to maintain optimal combustion temperatures.

Electrode Material: Iridium vs. Platinum vs. Copper

Modern vehicles like your 2015 Accord typically come equipped with long-life spark plugs, meaning they utilize precious metals for their electrodes. The primary types are:

• Iridium: This is the most common OEM choice for your Accord. Iridium is extremely hard and has a very high melting point, allowing for very fine electrodes. This design concentrates the spark, improving ignition efficiency and fuel economy, and extending the plug's lifespan to 100,000 miles or more.
• Platinum: While not as durable as iridium, platinum plugs also offer a significant lifespan advantage over traditional copper plugs, often rated for 60,000-80,000 miles. They are also a good choice for consistent performance.
• Copper: Copper spark plugs have excellent conductivity but are much softer, leading to faster wear of the electrode. They are generally only found in older vehicles or high-performance applications where frequent changes are acceptable. Your Accord is designed for long-life plugs, so copper plugs are not recommended.

Using the recommended iridium plugs will ensure your Accord maintains its intended performance and longevity.

How to gap a spark plug

While most modern iridium spark plugs come pre-gapped from the factory, it's always a good practice to double-check the gap before installation, especially for the 2015 Honda Accord. The correct gap allows for a strong, consistent spark.

To gap a spark plug:

1. Use a wire-type spark plug gapping tool: These tools are typically round with various wire diameters or a flat feeler gauge. Avoid using coin-style gappers, as they can damage the fine electrode of iridium plugs.
2. Measure the gap: Slide the appropriate wire diameter or feeler gauge between the center and ground electrodes. There should be a slight drag.
3. Adjust if necessary: If the gap is too small, gently bend the ground electrode outwards using the gapping tool's adjustment notch. If the gap is too large, carefully tap the ground electrode on a clean, solid surface to close it slightly. Be extremely careful not to touch or bend the delicate center iridium electrode.
4. Re-measure: Recheck the gap to ensure it meets the recommended specification (0.044 in / 1.1 mm for both Accord engines).

Replacement procedure tips

Replacing spark plugs on your 2015 Honda Accord is a manageable DIY task for most, but there are a few key tips specific to these engines (K24W1 2.4L I4 and J35Y2 3.5L V6):

• Coil-on-plug removal: Both engines utilize a coil-on-plug (COP) ignition system. Each spark plug has its own ignition coil directly on top of it. To access the plugs, you'll need to disconnect the electrical connector from each coil and then carefully unbolt and remove the coil. Be gentle with the connectors, as they can become brittle over time.
• Anti-seize debate: There's ongoing discussion about using anti-seize on spark plug threads. Most modern spark plugs (like those for your Honda) have a special coating on the threads, rendering anti-seize unnecessary and potentially leading to over-torqueing. Honda generally recommends not using anti-seize. If you do choose to use it, apply a very thin layer and reduce your torque specification by about 10-20% to avoid overtightening.
• Dielectric grease on boots: Applying a small amount of dielectric grease inside the spark plug boot (the rubber part of the coil that connects to the plug) can help prevent moisture intrusion, inhibit corrosion, and make future removal easier. Be careful not to get grease on the electrical contacts.
• Torque wrench is essential: The specified torque range of 11-14 lb-ft (15-19 Nm) is relatively low. Using a torque wrench is critical to prevent overtightening, which can strip threads in the cylinder head or damage the spark plug, and undertightening, which can cause the plug to loosen and lead to misfires.

Known issues

Fortunately, the 2015 Honda Accord engines (2.4L I4 K24W1 and 3.5L V6 J35Y2) are not known for any specific widespread spark plug-related issues like the Ford 3-valve engine's original two-piece plug breakage or GM's ionization-sensing coil problems. Honda's chosen spark plugs and engine designs are generally robust.

Need plugs replaced? Find a shop on Repairius.