2025 Chevrolet Silverado 1500 — Spark Plug Type & Gap

Quick reference

Note: All 2025 Silverado engines are expected to use the same ACDelco 12694178 spark plug, which is an iridium-tipped plug.

Why the right plug matters

Spark plugs are vital for your engine's performance, fuel efficiency, and emissions. Using the correct spark plug for your 2025 Chevrolet Silverado 1500 is not just a recommendation; it's essential for optimal operation and longevity. Here's why:

Heat Range: This refers to the plug's ability to dissipate heat from the combustion chamber. A "hotter" plug retains more heat, while a "colder" plug dissipates it faster. An incorrect heat range can lead to pre-ignition (detonation) or fouling, both of which can severely damage your engine. The OE spark plugs are carefully selected for the specific thermal characteristics of each Silverado engine.

Electrode Metal: The material of the spark plug electrode significantly impacts its lifespan and performance. The 2025 Silverado 1500 models, across various engine options, are designed to use iridium-tipped spark plugs from the factory. Iridium is an extremely durable and hard metal, allowing for a finer wire center electrode. This design provides a more concentrated spark and longer service intervals compared to platinum or copper plugs.

• Iridium: Offers the longest lifespan (up to 100,000 miles or more) and excellent performance due to its fine electrode. This is the OEM choice for your Silverado.
• Platinum: A good balance of performance and durability, typically lasting around 60,000-80,000 miles. Not typically an OEM choice for direct-injection engines like those in the Silverado 1500.
• Copper: The most conductive and cheapest, but also the least durable, usually requiring replacement every 15,000-30,000 miles. Not suitable for modern engines requiring extended service intervals.

How to gap a spark plug

While many modern iridium spark plugs come pre-gapped from the factory, it's always a good idea to verify the gap, especially if you're using an aftermarket plug. However, exercise extreme caution with iridium plugs due to their delicate fine-wire electrodes.

1. Use the correct tool: A wire-type spark plug gapping tool is essential. Avoid using coin-style gapping tools, especially on iridium plugs, as they can damage the delicate electrode.
2. Measure carefully: Gently slide the wire gauge into the spark plug gap. It should offer slight resistance.
3. Adjust gently (if necessary): If adjustment is needed, very carefully bend the ground electrode only. Never apply force to the center electrode, as it can easily break or damage the iridium tip. For iridium plugs, it's often recommended to avoid gapping unless absolutely necessary, or to consider them non-adjustable.
4. Re-check: After any adjustment, re-check the gap to ensure it meets the specifications for your engine.

Replacement procedure tips

Replacing spark plugs on your 2025 Chevrolet Silverado 1500 is a manageable DIY task for those with mechanical experience, but it requires patience and attention to detail. All current Silverado engines utilize a coil-on-plug (COP) ignition system.

1. Safety First: Disconnect the negative battery terminal before starting any electrical work.
2. Access: Depending on your engine, you may need to remove engine covers, air intake components, or other obstructions to gain clear access to the spark plugs.
3. Coil-on-Plug Removal: Each spark plug has its own ignition coil mounted directly on top. Carefully disconnect the electrical connector by pressing the release tab and pulling. Then, gently twist and pull upwards on the coil boot to remove the coil assembly. Avoid pulling directly on the wires.
4. Clean the Area: Before removing the old spark plugs, use compressed air to blow out any debris around the plug wells. This prevents dirt and grime from falling into the combustion chamber once the old plug is removed.
5. Anti-Seize Debate: There is much debate regarding the use of anti-seize on spark plug threads. For spark plugs with nickel-plated shells, like the OEM ACDelco plugs, anti-seize is generally not recommended. The plating provides adequate corrosion resistance and using anti-seize can lead to over-torquing the plugs, potentially damaging the cylinder head threads or the spark plug itself. Always refer to the spark plug manufacturer's recommendations.
6. Dielectric Grease: Apply a small amount of dielectric grease inside the spark plug boot (where the coil connects to the plug). This helps lubricate the boot for easier installation and removal, and also helps seal out moisture, preventing misfires.
7. Installation: Hand-thread the new spark plugs into the cylinder head to avoid cross-threading. Once finger-tight, use a torque wrench to tighten them to the manufacturer's specified torque (18 lb-ft / 24 Nm). Accurate torque is crucial; under-torquing can lead to loose plugs and misfires, while over-torquing can damage the cylinder head.
8. Reassembly: Reinstall the coil-on-plug assemblies, ensuring they "click" into place and the electrical connectors are securely fastened. Reinstall any removed air intake components or engine covers.

Known issues

Modern Chevrolet Silverado engines are generally robust, and specific widespread spark plug issues like those seen with some Ford 3-valve engines (e.g., cracked porcelain or two-piece plug breakage) are not commonly reported for the 2025 models. The direct injection and advanced ignition systems are designed for reliability and efficiency. However, always be vigilant for symptoms such as:

• Misfires: A rough idle, hesitation, or a check engine light flashing can indicate a misfire, often related to a faulty spark plug or ignition coil.
• Reduced Fuel Economy: Worn-out spark plugs can lead to inefficient combustion and a drop in MPG.
• Rough Idling or Stalling: Poor spark delivery can cause the engine to run unevenly.

Regular maintenance and using the correct OEM-specified spark plugs will help prevent most potential issues.

Need plugs replaced? Find a shop on Repairius.