2021 Nissan Altima Spark Plug Type & Gap

Quick Reference

Why the Right Plug Matters

Choosing the correct spark plug for your 2021 Nissan Altima is more critical than you might think. Spark plugs are not "one size fits all" components. Every engine has specific requirements for spark plug design, heat range, and electrode material, and using the wrong plug can lead to a host of problems, from decreased fuel economy and reduced performance to serious engine damage.

Heat Range: This refers to the plug's ability to dissipate heat. A "cold" plug dissipates heat quickly and is used in high-performance or forced-induction engines (like your Altima's VC-Turbo) to prevent pre-ignition. A "hot" plug retains more heat and is suitable for engines that operate at lower temperatures. Using a plug with the wrong heat range can lead to fouling (if too cold) or overheating and pre-ignition (if too hot).

Electrode Metal: The material of the center electrode significantly impacts the plug's lifespan and performance.

• Iridium: These are the most common type for modern vehicles, including your 2021 Altima. Iridium is incredibly strong and has a very high melting point, allowing for very fine electrodes that produce a precise and strong spark. This translates to excellent fuel efficiency, consistent performance, and extended replacement intervals (typically 60,000 to 105,000 miles).
• Platinum: While not typically found in the 2021 Altima as OEM, platinum plugs offer a longer lifespan than copper, but generally not as long as iridium. They use a platinum disc welded to the center electrode.
• Copper: These are the oldest and least expensive type. They have a large copper core, which provides excellent conductivity but wears down quickly, requiring more frequent replacement (typically 30,000 miles).

How to Gap a Spark Plug

While many iridium spark plugs come pre-gapped from the factory, it's always a good idea to double-check, especially if you're using an aftermarket plug. The spark plug gap is the distance between the center and ground electrodes. An incorrect gap can lead to misfires, rough idling, and poor fuel economy.

To gap a spark plug, you'll need a spark plug gapping tool, which can be a coin-style or wire-style gauge. For modern iridium plugs, which are very delicate, a wire-style gauge is preferred to avoid damaging the fine electrode.

1. Consult the specifications: Refer to the Quick Reference table above for the correct gap for your Altima's engine.
2. Measure the current gap: Carefully slide the appropriate wire gauge through the gap. It should offer slight resistance.
3. Adjust if necessary: If the gap is too small, use the gapping tool to gently widen it by leveraging it against the ground electrode. If the gap is too wide, carefully tap the ground electrode on a hard, non-abrasive surface to close it. Never bend the center electrode as this will likely damage the iridium tip.
4. Re-measure: Always re-measure to ensure the gap is correct before installation.

Replacement Procedure Tips for Your 2021 Nissan Altima

Changing spark plugs on your 2021 Nissan Altima is a relatively straightforward DIY task, but a few tips can make the job smoother.

1. Coil-on-Plug System: Your Altima utilizes a coil-on-plug (COP) ignition system, meaning each spark plug has its own individual ignition coil directly above it. To access the spark plugs, you'll need to disconnect the electrical connector from each coil and then remove the coil mounting bolt. Gently twist and pull to remove the coil from the spark plug well. Be careful not to pull on the wires.
2. Anti-Seize Debate: There's ongoing debate regarding the use of anti-seize compound on spark plug threads. Most modern spark plugs, especially nickel-plated ones like those used in the Altima, do not require anti-seize. Applying it can actually lead to over-torquing and damage to the cylinder head threads because anti-seize acts as a lubricant, altering the friction coefficient and throwing off torque wrench readings. Unless specifically recommended by the spark plug manufacturer, it's generally best to install modern spark plugs dry.
3. Dielectric Grease on Boots: A small amount of dielectric grease applied to the inside of the spark plug boot (the bottom part of the ignition coil that slides over the spark plug) can aid in future removal and help prevent moisture intrusion. Be careful not to get any grease on the actual electrode tip of the spark plug.
4. Torque is Crucial: Always use a torque wrench to tighten the new spark plugs to the manufacturer's specifications (see Quick Reference table). Over-tightening can damage the spark plug or, worse, the cylinder head threads. Under-tightening can lead to combustion gas leakage and overheating.
5. One at a Time: To avoid mixing up spark plug wires or coils, it's good practice to replace one spark plug at a time.

Known Issues

Fortunately, the 2021 Nissan Altima's engines (QR25DE and KR20DDET) do not have widespread, notorious spark plug-related issues like the Ford 3-valve engine's propensity for two-piece spark plug breakage. As long as you use the correct spark plugs and adhere to the recommended replacement intervals and procedures, you should experience trouble-free ignition.

Need plugs replaced? Find a shop on Repairius.