2020 GMC Yukon Spark Plug Guide

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2020 GMC Yukon is more than just a matter of finding a part that fits. It's about ensuring optimal engine performance, fuel efficiency, and longevity. The spark plug is a small but critical component, responsible for igniting the air-fuel mixture in each cylinder. Here's what you need to know about the key factors:

• Heat Range: A spark plug's heat range determines how quickly it dissipates heat from the combustion chamber. A plug that is too "hot" (doesn't dissipate heat fast enough) can lead to pre-ignition and engine damage. A "cold" plug (dissipates heat too quickly) can become fouled with carbon deposits, causing misfires. For the modern engines in your Yukon, sticking to the OEM-specified heat range is crucial for a smooth-running engine.

• Electrode Material:

  • Iridium: Your 2020 Yukon came from the factory with iridium-tipped spark plugs, and for good reason. Iridium is an extremely hard and durable precious metal, allowing for a very fine-wire center electrode. This creates a more focused and consistent spark, leading to better combustion and a longer lifespan – typically up to 100,000 miles. While they are the most expensive option, their longevity and performance make them the recommended choice.
  • Platinum: Platinum plugs were the long-life standard before iridium. They offer a good balance of performance and durability, often lasting 60,000 to 80,000 miles. Double platinum plugs, with platinum on both the center and ground electrodes, are a good alternative if iridium plugs are unavailable.
  • Copper: Copper plugs have a large-diameter nickel alloy electrode. They are excellent conductors and offer great performance, but they wear out much faster than iridium or platinum plugs, often needing replacement every 20,000 to 30,000 miles. They are not recommended for the 2020 GMC Yukon.

How to gap a spark plug

Even if you purchase pre-gapped plugs, it's always a good idea to double-check the gap before installation. A feeler gauge or a spark plug gap tool is essential for this. The correct gap for both the 5.3L and 6.2L engines in the 2020 Yukon is 0.040 inches (1.0 mm). To check the gap, slide the appropriate feeler gauge between the center and ground electrodes. It should slide through with a slight drag. If the gap is too wide, gently tap the ground electrode on a clean, hard surface to close it. If it's too narrow, use the hook on your gapping tool to gently pry it open. Be very careful not to damage the delicate iridium center electrode.

Replacement procedure tips

Replacing the spark plugs on your 2020 Yukon is a manageable DIY project with the right tools and a little patience. Both the 5.3L and 6.2L engines use a coil-on-plug ignition system, which means each spark plug has its own ignition coil mounted directly on top of it. Here are some tips:

• Coil-on-Plug Removal: To access the spark plugs, you must first remove the ignition coils. This is typically done by disconnecting the electrical connector and removing a single bolt holding the coil to the valve cover. Gently twist and pull the coil straight up to remove it.

• The Anti-Seize Debate: There is much debate in the automotive community about whether to use anti-seize on spark plug threads. The short answer is: it depends on the spark plug manufacturer. Some, like NGK, specifically advise against it, as their plugs are manufactured with a special coating that prevents seizing. If you do use anti-seize, use only a very small amount on the threads, and be aware that it can alter the torque reading, potentially leading to over-tightening.

• Dielectric Grease: It is highly recommended to apply a small amount of dielectric grease to the inside of the spark plug boot before reinstalling the ignition coil. This helps to seal out moisture and prevent corrosion, making it easier to remove the coil in the future.

Known issues

While the 2020 GMC Yukon engines are generally reliable, it's worth noting a couple of historical spark plug-related issues that have affected other manufacturers, though are not common on these specific engines:

• Cracked Porcelain: This has been a more significant issue on some Ford engines, particularly the 3-valve Triton engines, where the two-piece spark plug design could cause the porcelain insulator to crack during removal. While not a common problem on the GM LS-based engines in your Yukon, it's always a good practice to use a quality spark plug socket and a steady hand to avoid any potential damage.

• Broken Plug Shells: This can happen with any engine if the spark plugs are over-torqued or if they have been in the engine for too long and have seized in the cylinder head. Using a torque wrench and adhering to the 15 lb-ft (20 Nm) specification is the best way to prevent this.

Need plugs replaced? Find a shop on Repairius.