2020 GMC Acadia Spark Plug Specs: Type, Gap & Torque Guide

When it comes to maintaining your 2020 GMC Acadia, ensuring the ignition system is operating at peak efficiency is critical for fuel economy, smooth idling, and maximum power. The 2020 Acadia comes with three engine options—a 2.5L naturally aspirated inline-4, a 2.0L turbocharged inline-4, and the robust 3.6L V6. All of these engines utilize modern Coil-On-Plug (COP) ignition systems and come factory-equipped with long-life iridium spark plugs.

As an ASE-certified master technician, I’ve pulled hundreds of plugs out of modern GM engines. Putting the wrong plug in, or botching the torque or gap, can lead to misfires, check engine lights, and even damaged catalytic converters. Here is your definitive guide to spark plug specs for the 2020 GMC Acadia.

Quick reference

Note: Always verify the exact gap on your emissions decal under the hood, as slight mid-year production changes can occur.

Why the right plug matters

Modern engines like those in the 2020 Acadia are heavily reliant on precise ignition timing and robust spark energy.

• Electrode Metal: Your Acadia requires Iridium spark plugs. While copper plugs offer great conductivity, they will burn up within 20,000 miles in a modern high-compression, direct-injected engine. Platinum is a step up, but iridium is six times harder and eight times stronger than platinum, allowing it to withstand the extreme cylinder pressures of the 2.0L Turbo and 3.6L V6 for nearly 100,000 miles.
• Heat Range: Using the correct OEM heat range is non-negotiable. A plug that is too hot will cause pre-ignition (pinging) and potentially melt the piston. A plug that is too cold will foul out with carbon deposits, especially on direct-injected engines. Stick to the OEM ACDelco, NGK, or Denso equivalents listed above.

How to gap a spark plug

While most modern iridium spark plugs come pre-gapped from the factory, you must always verify the gap before installation. Dropped boxes in transit can easily close a gap.

1. Use the right tool: Do not use a cheap coin-style gauge on iridium plugs; sliding it aggressively can snap the fragile iridium center electrode. Use a wire-style feeler gauge.
2. Checking the gap: The correct wire size should pass through the gap with a slight "drag."
3. Adjusting the gap: If the gap is too tight, use a proper gap-adjusting tool to gently bend the ground strap up. Never pry against the center iridium tip. If it's too loose, gently tap the ground strap on a soft wooden workbench to close it.

Replacement procedure tips

Replacing plugs on the 2020 Acadia involves a coil-on-plug setup. Here are a few professional tips for these specific engines:

• 3.6L V6 Rear Bank Access: The front three plugs on the LGX V6 are a breeze, but the rear three are buried under the upper intake manifold (plenum). You will need to remove the intake plenum to access the rear bank coils. Make sure to purchase a new intake manifold gasket set before starting this job to prevent vacuum leaks upon reassembly.
• The Anti-Seize Debate: Modern ACDelco and NGK spark plugs feature a specialized trivalent metal plating that prevents seizing in the aluminum cylinder head. Do not use anti-seize on the threads. Adding anti-seize acts as a lubricant, which can easily cause you to over-torque the plug and strip the threads in your aluminum head.
• Dielectric Grease: Always apply a small dab of dielectric grease to the inside of the coil boot. This prevents the rubber boot from baking onto the porcelain of the new spark plug, making future removal much easier and sealing out moisture.

Known issues

While the 2020 Acadia doesn't suffer from the infamous broken 2-piece spark plug shell issues seen on older Ford 3-valve engines, there are a few things to watch out for:

• Direct Injection Carbon Fouling: All three Acadia engines are Direct Injected (SIDI). Since fuel doesn't wash over the intake valves, carbon can build up in the combustion chamber. If you experience misfires before the 97,500-mile interval, you may have carbon-fouled plugs.
• Brittle Coil Connectors: The plastic locking tabs on the coil-on-plug harness connectors become incredibly brittle from engine heat. Use a small pick tool to gently release the grey locking tabs. If you force them, they will snap, requiring a pigtail replacement.

Need plugs replaced? Find a shop on Repairius.