2018 GMC Acadia Spark Plug Specifications

Quick Reference

Why the Right Plug Matters

Choosing the correct spark plug is critical for engine health, performance, and fuel economy. It's not just about finding a plug that threads in; it's about heat range, electrode material, and design.

• Heat Range: This refers to how quickly the plug dissipates heat from its tip. A plug that is too "hot" (retains heat) can lead to pre-ignition (detonation), which is damaging to the engine. A plug that is too "cold" (dissipates heat too quickly) can foul with carbon deposits, leading to misfires. The original equipment (OE) plugs are designed for the specific heat range required by your Acadia's engine.
• Electrode Material: The 2018 Acadia, like most modern vehicles, uses iridium-tipped spark plugs from the factory. Iridium is an extremely hard and dense precious metal, which allows for a very fine center electrode. This fine wire design requires less voltage to create a spark, provides a more consistent spark, and is highly resistant to wear. While cheaper platinum or copper plugs might be available, they will have a significantly shorter lifespan and may not perform as well as the OE iridium plugs, which are designed to last 100,000 miles.

How to Gap a Spark Plug

Even though most modern iridium plugs come pre-gapped, it is crucial to verify the gap before installation. Shipping and handling can cause the delicate electrodes to get bent.

1. Use the Right Tool: Use a wire-style or feeler gauge tool. Do not use the old "ramp" style coin gauges, as they can put pressure on the fine-wire iridium tip and cause damage.
2. Check the Gap: Gently slide the correct wire gauge between the center and ground electrodes. For the 2.5L, this would be the 0.040" wire; for the 3.6L, it's the 0.043" wire. You should feel slight drag.
3. Adjust if Necessary: If the gap is incorrect, do not pry against the center electrode. Instead, gently bend the ground electrode (the L-shaped metal piece extending over the center) with the adjustment slot on your gapping tool to open or close the gap. Re-check until it is perfect.

Replacement Procedure Tips

The 2018 Acadia uses a modern coil-on-plug (COP) ignition system. This means each spark plug has its own individual ignition coil sitting directly on top of it. This design is efficient but requires care during service.

• Coil-on-Plug Removal: After removing the engine cover, you will see the ignition coils. Unplug the electrical connector from each coil, then remove the single hold-down bolt (typically a 10mm head). Gently twist and pull the coil straight up to remove it from the spark plug.
• The Anti-Seize Debate: Modern spark plugs, including the ACDelco originals for your Acadia, have a special trivalent or nickel plating that acts as an anti-seize coating. For this reason, neither GM nor NGK recommends using additional anti-seize compound on the threads. Applying it can lead to over-torquing the plug, as the lubricant reduces friction. Over-torquing can stretch the plug shell and damage the cylinder head threads.
• Dielectric Grease: It is highly recommended to apply a small amount of dielectric grease to the inside of the ignition coil boot before reinstalling it. This grease does not conduct electricity; instead, it seals out moisture, prevents corrosion, and makes it easier to remove the coils in the future.

Known Issues

Fortunately, the 2.5L and 3.6L engines in the 2018 Acadia are not known for widespread, systemic spark plug-related issues like the infamous Ford 3-valve plug breakage. The design is straightforward. By using the correct tools, following the torque specifications precisely, and not using anti-seize, you can avoid common problems like cracked porcelain or stripped threads.

Need plugs replaced? Find a shop on Repairius.