2015 GMC Yukon Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2015 GMC Yukon is more critical than you might think. Spark plugs are not a "one-size-fits-all" component; various factors like heat range, electrode material, and gap play a significant role in your engine's performance, fuel efficiency, and longevity.

Heat Range: This refers to the plug's ability to dissipate heat. A "hot" plug retains more heat and is suitable for engines that run cooler, preventing fouling. A "cold" plug dissipates heat quickly and is used in high-performance or hard-working engines to prevent pre-ignition. Using a plug with an incorrect heat range can lead to engine damage or poor performance.

Electrode Metal: The material of the center and ground electrodes directly impacts durability and spark consistency.

• Iridium: This is the hardest and most durable electrode material. Iridium plugs typically feature fine-wire electrodes, which require less voltage to fire and provide a strong, consistent spark. They offer the longest lifespan, making them ideal for modern engines like the L83 in your Yukon, which uses extended-life iridium plugs from the factory.
• Platinum: Platinum plugs are also durable and offer a longer lifespan than copper. They are often found in "double platinum" configurations, where both the center and ground electrodes have platinum pads, further extending their life.
• Copper: Copper plugs have excellent conductivity but are softer and wear out faster. They typically have a larger center electrode and a shorter lifespan, making them less common in late-model vehicles.

How to gap a spark plug

The gap between the center and ground electrodes is crucial for proper spark ignition. The specified gap allows for the optimal spark to ignite the air-fuel mixture. Even though many modern iridium plugs are "pre-gapped" from the factory, it's always a good idea to double-check the gap before installation, especially for the high-precision requirements of today's engines.

To gap a spark plug:

1. Use the right tool: A wire-type feeler gauge is recommended for iridium and platinum plugs to avoid damaging the fine electrode. Avoid using a coin-style gapping tool, as it can be too aggressive.
2. Measure carefully: Slide the appropriate feeler gauge wire through the gap. There should be a slight drag.
3. Adjust if necessary: If the gap is too small, gently pry the ground electrode open with the gapping tool. If it's too wide, carefully tap the ground electrode on a clean, hard surface to close the gap slightly. Be extremely gentle, as excessive force can damage the electrode or insulator.

For your 2015 GMC Yukon's 5.3L L83 engine, the recommended gap is 0.040 inches (1.0 mm).

Replacement procedure tips

The 2015 GMC Yukon with the 5.3L V8 (L83) engine utilizes a coil-on-plug (COP) ignition system, meaning each spark plug has its own individual ignition coil mounted directly above it. This design provides a hotter, more precise spark.

• Coil-on-plug removal: Start by disconnecting the battery. Carefully disconnect the electrical connector from each ignition coil. Then, remove the bolt securing the coil to the valve cover (usually a 7mm or 10mm bolt). Gently twist and pull the coil straight up to remove it from the spark plug well. Avoid yanking or prying, as this can damage the coil or the rubber boot.
• Anti-seize debate: There's ongoing debate about using anti-seize compound on spark plug threads. For modern spark plugs with nickel-plated shells, manufacturers like ACDelco and NGK often advise against using anti-seize. The nickel plating acts as an anti-seize in itself, and adding more can lead to over-torquing the plug, potentially damaging the cylinder head threads or stretching the plug shell. When in doubt, follow the plug manufacturer's recommendations. If you choose to use anti-seize, sparingly apply a very thin coat and reduce the torque spec by approximately 10-20%.
• Dielectric grease on boots: Before reinstalling the ignition coils, apply a small amount of dielectric grease inside the rubber boot that connects to the spark plug. This helps prevent moisture intrusion, insulates against voltage leaks, and makes future removal easier.

Known issues

Fortunately, the 2015 GMC Yukon's 5.3L L83 engine is not known for widespread, unique spark plug-related issues like the Ford 3-valve 2-piece plug breakage. However, like any engine, regular maintenance is key.

One general consideration with GM's modern V8 engines, including the L83, is the sensitive ignition system. Aftermarket spark plugs that deviate significantly from the OEM specifications in terms of heat range or design can sometimes lead to misfires or codes, especially with systems that include ionization sensing (though less common on the L83). Sticking with the recommended OEM ACDelco plugs or high-quality aftermarket equivalents from NGK or Denso is highly advisable.

Need plugs replaced? Find a shop on Repairius.