2016 GMC Acadia Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2016 GMC Acadia is crucial for optimal engine performance, fuel efficiency, and longevity. Spark plugs are designed with specific heat ranges and electrode materials to match the demands of your engine. Using the wrong plug can lead to issues like misfires, reduced power, poor fuel economy, and even engine damage.

Heat Range: The heat range refers to the spark plug's ability to dissipate heat from the combustion chamber. A "cold" plug dissipates heat quickly and is suitable for high-performance engines or heavy-duty use, preventing pre-ignition. A "hot" plug retains heat longer, ideal for lower-performance engines to prevent fouling. Your Acadia's 3.6L V6 is designed for a specific heat range, so sticking to the recommended plug ensures proper combustion temperature.

Electrode Metal: The material of the spark plug electrode significantly impacts its lifespan and performance.

• Iridium: This is the most common and recommended material for modern vehicles like your Acadia. Iridium plugs have extremely fine electrodes and offer excellent durability, lasting up to 100,000 miles. They provide a strong, consistent spark and improved fuel efficiency.
• Platinum: Platinum plugs are also long-lasting, typically rated for 60,000 to 100,000 miles. They offer good performance but are generally a step below iridium in terms of ultimate durability and spark consistency.
• Copper: Copper plugs have a large-diameter copper core and are excellent conductors, but their soft electrodes wear quickly, usually requiring replacement every 15,000 to 30,000 miles. While cheaper, they are not suitable for modern engines like the one in your Acadia due to their short lifespan and inability to maintain optimum performance over extended periods.

How to gap a spark plug

The spark plug gap is the distance between the center and ground electrodes. An incorrect gap can lead to misfires, engine hesitation, and reduced power. For your 2016 GMC Acadia, the recommended gap is 0.043 inches (1.1 mm).

To gap a spark plug, you'll need a spark plug gap tool (either a coin-style or wire-gauge type). If the gap is too small, you can gently bend the ground electrode outwards. If the gap is too large, carefully tap the ground electrode on a hard surface to close it. Always re-check the gap after bending to ensure accuracy. Be extremely careful not to apply leverage to or touch the center electrode, especially on iridium plugs, as it can be very fragile and easily damaged.

Note: Many modern iridium spark plugs come pre-gapped from the factory. While it's always wise to double-check, avoid adjusting the gap on fine-wire iridium plugs unless absolutely necessary, as it's easy to damage the delicate electrode.

Replacement procedure tips for the 3.6L V6 (LLT)

Replacing spark plugs on your 2016 GMC Acadia's 3.6L V6 engine is a manageable DIY task, but careful attention to detail is key.

1. Coil-on-Plug Removal: Your Acadia uses a coil-on-plug (COP) ignition system. Each spark plug has its own ignition coil directly mounted above it. To access the plugs, you'll need to disconnect the electrical connector from each coil pack and then remove the bolt (usually a 10mm) securing the coil. Gently pull the coil straight up to remove it. Avoid yanking on the electrical connectors.
2. Accessing Rear Plugs: The rear bank of cylinders (closest to the firewall) can be more challenging to access. You may need to remove air intake components or other obstructions to gain better access. A universal joint or wobble extension for your ratchet can be very helpful here.
3. Anti-Seize Debate: Some technicians apply a small amount of anti-seize compound to the spark plug threads, while others advise against it, especially with nickel-plated spark plugs. ACDelco and other manufacturers often advise against it, as it can alter torque readings and potentially lead to over-tightening or issues with the plug's electrical grounding. If you choose to use it, apply an extremely thin coat and reduce the specified torque by about 10-20%.
4. Dielectric Grease on Boots: A small dab of dielectric grease inside the spark plug boot (the rubber part of the coil pack that goes over the plug) is highly recommended. This helps to seal out moisture, prevents the boot from sticking to the plug's porcelain, and aids in easier removal next time. Do not apply dielectric grease to the spark plug tip or electrodes.
5. Torque is Crucial: Over-tightening spark plugs can damage the cylinder head threads, while under-tightening can lead to compression leaks and misfires. Always use a torque wrench and adhere to the specified 15 lb-ft (20 Nm). This is especially important for aluminum cylinder heads.
6. One at a Time: It's often a good practice to replace one spark plug at a time. This prevents cross-contamination of foreign objects into the engine and ensures you don't accidentally mix up spark plug wires or coil packs (though less of an issue with COP systems).

Known issues (N/A)

Fortunately, the 3.6L V6 (LLT) engine in the 2016 GMC Acadia is not known for widespread or specific spark plug-related issues like the Ford 3-valve engine's propensity for broken two-piece plugs. As long as the correct ACDelco 41-109 (or equivalent iridium) spark plugs are used and replaced within the recommended 100,000-mile interval, you should experience reliable performance.

Need plugs replaced? Find a shop on Repairius.