2024 Chevrolet Silverado 2500HD Spark Plug Type & Gap Specs

When it comes to the heavy-lifting capabilities of the 2024 Chevrolet Silverado 2500HD, maintaining peak engine performance is non-negotiable. Whether you are hauling heavy equipment or towing a fifth-wheel trailer, your engine’s ignition system works overtime. As an ASE-certified master technician, I regularly see how critical proper spark plug maintenance is for these heavy-duty trucks.

For the 2024 Silverado 2500HD, there are two engine options: the 6.6L Duramax V8 Turbodiesel (which uses glow plugs, not spark plugs) and the 6.6L L8T Gas V8. Below is the comprehensive guide to servicing the spark plugs on the 6.6L Gas V8.

Quick reference

Note: Always verify exact part numbers with your VIN as manufacturers occasionally update supercessions during the model year.

Why the right plug matters

Using the correct spark plug is vital for engine efficiency, emission control, and preventing catastrophic damage. Modern GM engines like the 6.6L L8T rely on precise heat ranges to draw heat away from the firing tip. If a plug is too "hot," it can cause pre-ignition and engine knock; too "cold," and it will foul out with carbon deposits.

The factory ACDelco 41-162 is an iridium spark plug. Unlike traditional copper or older platinum plugs, iridium is incredibly dense and has a much higher melting point. This allows the center electrode to be wire-fine, concentrating the electrical charge for a more efficient spark while easily lasting up to the nearly 100,000-mile service interval. Downgrading to copper or platinum will drastically reduce your service interval and can lead to misfires under heavy towing loads.

How to gap a spark plug

Modern iridium spark plugs typically come pre-gapped, but a master tech never installs a plug without verifying the gap first—shipping drops happen.

1. Use the right tool: Do not use a cheap coin-style gauge on iridium plugs, as sliding it through can snap the fragile iridium tip. Use a wire-style feeler gauge instead.
2. Check the gap: Gently pass the 0.040" (1.0 mm) wire between the center and ground electrode. It should have a light drag.
3. Adjust carefully: If the gap is too tight, use the bending notch on your gapping tool to lightly bend the ground strap away from the center electrode. Never pry against the center iridium electrode.

Replacement procedure tips

The 6.6L L8T utilizes a Coil-on-Plug (COP) style ignition system with short ignition wires connecting the coil pack to the plug.

• Access: The passenger side rear plugs can be a bit tight against the firewall. A swivel socket and various extensions will be your best friends here.
• The Anti-Seize Debate: GM's official service manual dictates that modern ACDelco spark plugs feature a nickel-plated shell designed to prevent seizing in the aluminum cylinder heads. Adding anti-seize acts as a lubricant, which can cause you to over-torque the plug and strip the aluminum threads. Do not use anti-seize.
• Dielectric Grease: Apply a very small dab of dielectric grease to the inside of the spark plug wire boots. This prevents moisture intrusion, stops voltage leaks, and ensures the boot won't weld itself to the ceramic porcelain over the next 100,000 miles.

Known issues

While the 2024 6.6L L8T avoids the infamous broken two-piece spark plug shell issues that plagued older Ford 3-valve engines, it does have its quirks.

The most common issue encountered during maintenance is heat-welded spark plug wire boots. Because of the extreme under-hood temperatures—especially when the truck is used for heavy towing—the rubber boots can bake onto the plug's porcelain. Attempting to yank them off by the wire will break the internal conductor. Always use specialized spark plug boot pliers to grab the base of the boot, give it a firm twist to break the seal, and then pull straight back.

Need plugs replaced? Find a shop on Repairius.