2015 Chevrolet Silverado 2500HD Spark Plug Specs: Type, Gap & Torque

When it comes to keeping your heavy-duty workhorse running strong, ignition maintenance is non-negotiable. For the 2015 Chevrolet Silverado 2500HD, the only engine equipped with spark plugs is the 6.0L Vortec V8 (L96 Gas/Flex-Fuel and LC8 Bi-Fuel CNG). The mighty 6.6L Duramax is a diesel, relying on compression and glow plugs, so if you are driving the diesel, you can skip this guide!

For the 6.0L V8 owners, swapping out spark plugs at the right interval using the correct specifications will restore fuel economy, smooth out your idle, and prevent misfires under heavy towing loads. Here is your definitive guide.

Quick reference

Why the right plug matters

Modern engines are incredibly sensitive to spark plug design. You cannot simply grab any plug off the shelf that threads into the hole.

Heat Range: The heat range determines how fast the spark plug pulls heat away from its tip and transfers it into the cylinder head. Using a plug that is too hot can cause pre-ignition and catastrophic engine knock, while a plug that is too cold will foul out with carbon deposits. Always stick to the OEM heat range unless you have heavily modified the engine.

Electrode Metal:

• Iridium: The gold standard for modern engines and the OEM requirement for the 2015 Silverado 2500HD. Iridium is extremely hard, allowing for a fine-wire center electrode that fires with less voltage while lasting up to 100,000 miles.
• Platinum: Good durability, but slightly less conductive and durable than iridium.
• Copper: Highly conductive but wears out rapidly (usually in 15,000 to 30,000 miles).

For the 6.0L V8, you should always use the factory-spec double-iridium plugs. Downgrading to copper or platinum will severely reduce the lifespan of the plug and potentially strain the coil packs.

How to gap a spark plug

Even if ACDelco 41-110 plugs are advertised as "pre-gapped," shipping and handling can bump the ground electrode. You should always verify the gap before installation.

1. Use the Right Tool: Use a wire-type gauge or a specialized feeler gauge. Coin-style ramp gauges can easily damage the delicate fine-wire iridium tip.
2. Measure: Gently pass the 0.040 in (1.01 mm) wire through the gap. It should pass through with a slight "drag."
3. Adjust (If Necessary): Never pry against the center electrode! Use a spark plug gapping tool with a bending slot to gently tweak the ground strap. Lightly bend it away from the center to widen the gap, or tap it on a soft wooden workbench to close it. Re-measure until perfectly set at 0.040 inches.

Replacement procedure tips

The 6.0L Vortec uses a "coil-near-plug" setup rather than true coil-on-plug or an older distributor system. Each cylinder has an individual ignition coil mounted on the valve cover, connected to the spark plug via a short ignition wire.

• Wire Removal: The metal heat shields on the plug boots can make them stubborn. Twist the boot slightly to break the seal before pulling. Pull from the boot, not the wire itself, to avoid tearing the internal conductor.
• The Anti-Seize Debate: ACDelco explicitly states do not use anti-seize on their 41-110 plugs. Modern ACDelco and NGK plugs feature a special nickel or zinc-chromate plating that acts as a release agent. Adding anti-seize alters the friction coefficient, causing you to over-torque the plug and potentially damage the aluminum cylinder head threads.
• Dielectric Grease: Apply a small dab of dielectric grease to the inside of the spark plug wire boots. This prevents moisture intrusion, stops high-voltage tracking, and ensures the boots will come off easily during the next tune-up.
• Torque Spec: Thread the plugs in by hand to ensure they aren’t cross-threading. Tighten them to 11 lb-ft (15 Nm). Do not over-tighten!

Known issues

While you won't face the infamous broken 2-piece spark plug shell issues that plague older Ford 3-valve engines, the Chevy 6.0L has a couple of quirks:

• Cracked Porcelain: The rear passenger side plug (Cylinder 8) is notoriously tight against the firewall. Technicians often put lateral pressure on the socket extension when loosening or tightening this plug. This side-loading easily cracks the ceramic porcelain, leading to an immediate misfire. Use a swivel socket or a wobble extension, and keep your tool perfectly in line with the plug.
• Seized Plugs in Aluminum Heads: Even with coated plugs, leaving them in the engine past 100,000 miles can lead to carbon build-up on the exposed threads in the combustion chamber. If a plug feels excessively tight when removing it, stop. Spray penetrating oil down the tube, thread it back in slightly, and work it back and forth to clear the threads without galling the aluminum head.

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