2018 Nissan Altima Spark Plug Type, Gap & Torque Specs

As an ASE-certified master technician, I can tell you that keeping the ignition system on your 2018 Nissan Altima in top shape is one of the easiest ways to maintain fuel economy and performance. Whether you are driving the highly popular 2.5L inline-4 or the robust 3.5L V6, Nissan’s modern coil-on-plug ignition systems are designed for high efficiency and longevity. Both engines use premium iridium-tipped spark plugs straight from the factory, which provide excellent wear resistance.

Below, you will find the exact specifications, part numbers, and expert tips you need to confidently replace the spark plugs on your 2018 Altima.

Quick reference

Why the right plug matters

Modern engines are incredibly sensitive to spark plug variations. Choosing the correct spark plug involves more than just finding one with matching threads.

Heat Range: The heat range dictates how fast the plug dissipates heat from the firing tip into the cylinder head. If you use a plug that is too hot, you risk pre-ignition and engine knock. Too cold, and the plug will foul with carbon. Electrode Metal: Your 2018 Nissan Altima comes factory-equipped with Iridium spark plugs. While you might be tempted to save a few dollars by installing cheaper platinum or copper plugs, do not do it. Iridium has a much higher melting point and is significantly stronger, allowing for the ultra-fine wire center electrode necessary to properly fire the Altima's lean air-fuel mixtures. Copper plugs would burn up well before the 105,000-mile interval.

How to gap a spark plug

Even though premium iridium plugs like the NGK DILHA12A11 come pre-gapped from the factory at 0.043 inches (1.1mm), you should always verify the gap before installation in case the plug was dropped during shipping.

1. Use the right tool: For fine-wire iridium plugs, never use a traditional coin-style gapping tool, as the heavy wedge can snap the fragile iridium tip. Use a wire-style feeler gauge instead.
2. Measuring: Gently pass the 0.043" wire between the center and ground electrode. It should slide through with a slight drag.
3. Adjusting: If the gap is too tight, use the bending notch on the gauge tool to gently pull the ground strap back. Never pry against the center electrode!

Replacement procedure tips

Replacing plugs on the 2018 Altima involves a coil-on-plug (COP) architecture, meaning there are no spark plug wires or distributors. Each cylinder has its own ignition coil sitting directly on top of the plug.

• 2.5L Access: The 4-cylinder is straightforward. Simply remove the engine cover, unbolt the 10mm coil hold-down bolts, pull the coils out, and use a 14mm thin-wall spark plug socket.
• 3.5L Access: The V6 is more labor-intensive. The upper intake manifold (plenum) must be removed to access the rear three spark plugs near the firewall. Make sure to purchase a new intake manifold gasket before starting the job to prevent vacuum leaks upon reassembly.
• Anti-Seize Debate: NGK and Denso explicitly state not to use anti-seize on their modern spark plugs. The threads feature a special trivalent metal plating that acts as a release agent. Adding anti-seize acts as a lubricant and can easily cause you to over-torque the plug, potentially damaging the aluminum cylinder head.
• Dielectric Grease: Apply a small pea-sized amount of dielectric grease to the inside of the ignition coil boot before reinstalling. This prevents moisture intrusion, prevents voltage leaks, and makes the boot easier to remove next time.

Known issues

Unlike the infamous Ford 3-valve engines known for snapping 2-piece plug shells in the head, the Nissan QR25DE and VQ35DE engines are highly reliable when it comes to plug extraction.

However, a known issue to watch out for on the 2.5L engine is oil pooling in the spark plug tubes. When pulling out the ignition coils, inspect the rubber boots for fresh engine oil. If they are dripping wet, your valve cover gasket's spark plug tube seals have failed. The entire valve cover often needs to be replaced as an assembly to fix this leak. Ignoring this will eventually cause the coil to short out, resulting in a misfire and a flashing check engine light.

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