2018 Honda Civic Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2018 Honda Civic is crucial for optimal engine performance, fuel efficiency, and longevity. Modern engines are highly sensitive to spark plug specifications, and using the wrong plug can lead to misfires, reduced power, increased emissions, and even engine damage.

Heat Range

Spark plugs are designed with a specific "heat range," which refers to their ability to dissipate heat from the combustion chamber. A plug that is too "hot" (dissipates heat slowly) can lead to pre-ignition and detonation, severely damaging your engine. A plug that is too "cold" (dissipates heat too quickly) can foul with carbon deposits, causing misfires and poor performance. Honda engineers have meticulously selected the correct heat range for each engine in your Civic, so always stick to the recommended OEM or equivalent plugs.

Electrode Metal (Iridium vs. Platinum vs. Copper)

• Iridium: The OEM plugs for your 2018 Honda Civic are typically iridium-tipped. Iridium is an extremely hard and durable metal with a very high melting point, allowing for fine-wire electrodes. This design provides a strong, consistent spark and exceptional longevity, usually rated for 100,000 miles or more.
• Platinum: Platinum plugs are also durable and offer good longevity, often rated for 60,000-100,000 miles. They are a step up from copper but generally not as long-lasting or efficient as iridium for modern engines requiring precision ignition.
• Copper: Copper plugs have a large-diameter copper core for excellent conductivity, but copper is a soft metal. While great for older, high-performance engines that require frequent spark plug changes, they are not suitable for the extended service intervals of modern vehicles like your Civic.

For your 2018 Civic, always opt for iridium plugs to match the factory specifications and achieve the intended service life and performance.

How to gap a spark plug

While virtually all iridium spark plugs come pre-gapped from the factory, it's a good practice to double-check the gap before installation. However, be extremely careful when gapping iridium plugs due to their fine-wire electrodes, which can be easily damaged.

1. Use a wire-style gap gauge: Never use a ramp-style or coin-style gauge, as these can chip or damage the iridium tip. A wire-style gauge allows you to measure the gap without applying undue force to the center electrode.
2. Verify the gap: Gently slide the correct wire gauge between the center and ground electrodes. There should be a slight drag.
3. Adjust if necessary (with extreme caution): If the gap needs adjustment, gently bend the ground electrode only. Never pry or bend the center electrode. For iridium plugs, it's often better to exchange a poorly gapped plug than to risk damaging it during adjustment.

Remember, your Honda Civic's recommended gap is 0.043 inches (1.1 mm).

Replacement procedure tips

Replacing spark plugs on your 2018 Honda Civic, whether it's the 1.5L turbo or 2.0L naturally aspirated engine, is a straightforward DIY task for moderately experienced individuals. Both engines utilize a coil-on-plug (COP) ignition system.

1. Gather your tools: You'll need a ratchet, appropriate extensions, a 10mm socket for coil pack bolts, and a 14mm or 5/8-inch spark plug socket (depending on the plug). A magnetic or rubber-inserted spark plug socket is highly recommended to prevent dropping plugs.
2. Access the coil packs: On both engines, the coil packs are easily accessible on top of the valve cover. Disconnect the electrical connector by pressing the tab and pulling. Then, unbolt the coil pack (typically 10mm bolt) and gently twist and pull to remove it from the spark plug well.
3. Remove the old plugs: Use your spark plug socket and extension to carefully loosen and remove the old spark plugs. Turn counter-clockwise. Ensure the socket seats properly before applying force.
4. Anti-seize debate: There is an ongoing debate about using anti-seize on spark plug threads. Most modern spark plugs feature a special coating that serves the same purpose. Applying anti-seize to coated plugs can alter the torque readings, leading to over-tightening and potentially stripped threads. Honda typically does not recommend anti-seize for their factory plugs. If you choose to use it, apply a very thin amount to the threads only, avoiding the electrode, and reduce the specified torque by about 10-20%.
5. Install new plugs: Thread the new spark plugs in by hand first to prevent cross-threading. Once finger-tight, use a torque wrench to tighten them to the specified 13 lb-ft (18 Nm). Over-tightening can damage the spark plug and cylinder head threads.
6. Dielectric grease on boots: Apply a small amount of dielectric grease inside the rubber boot of each coil pack. This helps seal out moisture, prevents the boot from sticking to the plug, and aids in electrical insulation.
7. Reinstall coil packs: Push the coil packs firmly onto the new spark plugs until they seat. Reinstall the mounting bolts and reconnect the electrical connectors until they click.

Known issues

Fortunately, the 2018 Honda Civic engines (1.5L Turbo and 2.0L Non-Turbo) do not have widespread, notorious spark plug-related issues akin to the Ford 3-valve Triton engine