2015 Chevrolet Silverado 3500HD Spark Plug Type, Gap & Torque Specs

When it comes to maintaining a heavy-duty workhorse like the 2015 Chevrolet Silverado 3500HD, keeping the ignition system in top shape is critical. Whether you're hauling heavy loads or towing a fifth wheel, your engine needs consistent, powerful spark to operate efficiently. Note that while the 3500HD was available with the 6.6L Duramax diesel (which uses glow plugs, not spark plugs), the gas-powered workhorses feature the ultra-reliable 6.0L V8 (L96).

As an ASE-certified master technician, I've seen firsthand what happens when the wrong plugs are installed or improper gaps are used. Here is your definitive guide to the spark plug specifications, gaps, and torque requirements for the gas-powered 2015 Chevy Silverado 3500HD.

Quick Reference

*Note: ACDelco 41-162 is the updated GM part number that replaces the older 41-110.

Why the Right Plug Matters

Choosing the correct spark plug is more than just matching threads. The 6.0L V8 in the 3500HD operates under extreme load, making the heat range of the plug incredibly important. The heat range determines how fast the spark plug transfers heat away from its tip and into the cylinder head. Using a plug that runs too hot can cause pre-ignition and engine knock, while a plug that runs too cold will foul out with carbon.

Furthermore, electrode metal makes a massive difference. Modern GM V8 engines are designed strictly for Iridium spark plugs. Iridium is significantly harder and more durable than platinum or standard copper, allowing the plugs to easily survive their nearly 100k-mile service intervals without the electrode wearing down and widening the gap.

How to Gap a Spark Plug

Even though premium iridium plugs usually come pre-gapped, it is an absolute necessity to verify the gap before installation. A plug dropped in shipping can easily have its gap closed.

1. Use the right tool: Always use a wire-style or feeler gauge. Avoid the cheap coin-style gauges, as they can easily snap the ultra-fine iridium center electrode.
2. Measure gently: Slide the 0.040" wire between the center electrode and the ground strap. It should have a light "drag" but not force the gap open.
3. Adjusting the gap: If the gap needs widening or narrowing, use a dedicated gaping tool to gently bend the ground strap. Never pry against the fragile iridium center electrode.

Replacement Procedure Tips

The 6.0L V8 uses a coil-near-plug ignition system. Instead of the coil sitting directly on the spark plug, the coil is mounted to the valve cover and a short spark plug wire connects them.

• Wire Removal: Always twist the spark plug boot side-to-side before pulling it off. Pulling straight out will almost certainly rip the internal terminal out of the wire.
• The Anti-Seize Debate: GM officially recommends against using anti-seize on modern ACDelco spark plugs. The threads feature a special nickel coating designed to prevent galling in the aluminum cylinder heads. Adding anti-seize acts as a lubricant, which often leads to over-torquing and cracking the plug shell or damaging the cylinder head threads.
• Dielectric Grease: Apply a small dab of dielectric grease to the inside of the spark plug wire boots before snapping them back onto the new plugs. This prevents moisture intrusion, stops high-voltage tracking, and ensures the boots won't weld themselves to the porcelain over the next 100,000 miles.

Known Issues

While the 6.0L V8 doesn't suffer from the infamous 2-piece spark plug breakage common to older Ford 3-valve engines, there are a few things to watch out for. First, the exhaust manifolds on these trucks run incredibly hot under towing loads. It's very common for the heat shields around the spark plug boots to become brittle, and the spark plug wires themselves tend to bake onto the plugs. It is highly recommended to replace the spark plug wires simultaneously with the plugs on a 3500HD.

Additionally, if a plug is over-torqued past the 11 lb-ft specification, the porcelain insulator can easily crack. This micro-crack will allow the spark to arc directly to the engine block, causing a severe misfire under load. Always use a calibrated torque wrench.

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