2023 GMC Sierra 1500 Spark Plug Specs, Gap, and Torque Guide

As an ASE-certified master technician, I can tell you that replacing the spark plugs on a modern truck like the 2023 GMC Sierra 1500 is a critical maintenance item that shouldn't be ignored. Whether you're hauling heavy loads with the 6.2L V8, relying on the trusty 5.3L, or enjoying the torque of the 2.7L High Output Turbo, keeping your ignition system in top shape ensures you get maximum power and fuel economy.

(Note: The 3.0L Duramax inline-six is a diesel engine and uses glow plugs, not spark plugs, so it is omitted from this guide.)

Quick reference: 2023 GMC Sierra 1500 Spark Plug Specs

Why the right plug matters

Modern General Motors engines are incredibly sensitive to ignition performance. Using the right spark plug means matching the exact heat range and electrode material specified by the factory. The 2023 Sierra engines require iridium spark plugs.

Iridium is significantly harder and more durable than platinum or standard copper, allowing for an extremely fine wire center electrode. This concentrates the electrical charge, requiring less voltage to jump the gap while providing a cleaner, more consistent burn. While copper plugs offer excellent conductivity, they will wear out in a fraction of the time (often under 20,000 miles) and should never be used in a modern Sierra. Additionally, installing a plug with the wrong heat range can lead to pre-ignition (pinging) if it runs too hot, or carbon fouling if it runs too cold.

How to gap a spark plug

Most ACDelco iridium plugs come pre-gapped from the factory. However, as any seasoned technician will warn you, you must always verify the gap before installation in case the plug was dropped during shipping.

1. Use the right tool: Do not use the old-school coin-style gapping tool on iridium plugs, as it can easily snap the brittle, fine-wire center electrode. Use a wire-style feeler gauge.
2. Measure gently: Slide the correct size wire between the center and ground electrode. It should pass through with a light "drag."
3. Adjust carefully: If the gap is too tight, use the bending tool on the gauge to gently pry the ground strap up. If it is too wide, lightly tap the ground strap against a solid surface to close it. Never put pressure on the center electrode itself.

Replacement procedure tips

Replacing plugs on the 2023 Sierra is generally straightforward, but there are a few professional tricks to ensure success:

• Coil-on-Plug Systems: All 2023 Sierra gas engines use coil-on-plug (COP) ignition. Remove the 10mm bolt holding the coil pack, twist slightly to break the seal, and pull straight up.
• The Anti-Seize Debate: General Motors expressly recommends against using anti-seize compound on the spark plug threads. ACDelco plugs feature a special zinc/nickel coating that prevents seizing. Adding anti-seize acts as a lubricant, which can easily cause you to over-torque the plug and strip the aluminum cylinder head threads.
• Dielectric Grease: Always apply a small dab of dielectric grease to the inside of the spark plug boot before reattaching the coil. This prevents moisture intrusion, stops voltage leaks, and ensures the rubber boot won't bake onto the porcelain over the next 100,000 miles.
• Cold Engine Only: Only remove spark plugs when the engine is completely cold to prevent thread damage in the aluminum heads.

Known issues

While the 2023 Sierra doesn't suffer from the notorious broken-plug issues that plagued early-2000s Ford 3-valve engines, GM engines do have a quirk you should know about.

The 5.3L and 6.2L V8 engines use the ignition coils to monitor for misfires and engine knock through a process called "ionization sensing." If you use an improper aftermarket spark plug or a cheap replacement ignition coil, the resistance values will be slightly off. This can confuse the Engine Control Module (ECM), leading to false misfire codes (P0300) or erratic engine behavior. Stick to OEM ACDelco, NGK, or Denso components to avoid this headache.

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