2017 Chevrolet Silverado 3500HD Spark Plug Type, Gap & Torque Specs

The 2017 Chevrolet Silverado 3500HD is a heavy-duty workhorse. While many of these trucks left the factory with the legendary 6.6L Duramax diesel engine (which uses glow plugs, not spark plugs), a large number were equipped with the highly reliable 6.0L Vortec V8 (L96) gasoline engine. Maintaining this engine with the correct spark plugs ensures optimal towing performance, fuel economy, and smooth idling.

As an ASE-certified master technician, I've outlined everything you need to know about replacing the spark plugs on your 2017 Silverado 3500HD 6.0L V8.

Quick reference

Why the right plug matters

Modern heavy-duty engines like the 6.0L V8 are highly sensitive to spark plug specifications. Using the correct heat range and electrode material is non-negotiable.

The 6.0L L96 engine calls for iridium spark plugs from the factory. Iridium is significantly harder and more durable than platinum or standard copper, allowing the plug to withstand the high combustion temperatures of a heavy-duty engine while maintaining a sharp electrode edge for up to 100,000 miles. Downgrading to a copper or standard platinum plug will not only require much more frequent replacements but can also lead to misfires under heavy towing loads.

How to gap a spark plug

While modern ACDelco and premium NGK/Denso iridium plugs usually come pre-gapped, you should always verify the gap before installation. Dropped boxes in transit can easily close the gap.

1. Use the right tool: For precious metal plugs like iridium, use a wire-type gauge rather than a cheap coin-style gauge. Coin gauges can easily snap off the fragile iridium center electrode.
2. Measure gently: Pass the 0.040 in (1.01 mm) wire through the gap. It should pass through with a slight "drag."
3. Adjusting (if necessary): If the gap is too tight, use the bending tool on your gauge to carefully pull back the ground strap. Never pry against the center electrode.

Replacement procedure tips

The 6.0L V8 features a Coil-on-Plug (COP) ignition system (specifically, coil-near-plug with short ignition wires).

• Coil and Wire Removal: Twist the spark plug boots slightly before pulling to break the heat seal. Pulling blindly on the wire often results in a torn silicone boot.
• The Anti-Seize Debate: Most modern OEM ACDelco and premium aftermarket plugs feature a special nickel-plated shell designed to prevent seizing in the aluminum cylinder head. Do not use anti-seize on these plugs. Adding a liquid lubricant alters the torque readings, making it very easy to over-torque the plug and strip the cylinder head threads.
• Dielectric Grease: Apply a small pea-sized amount of dielectric grease to the inside of the spark plug boot before reinstallation. This prevents moisture intrusion and makes future removal much easier.
• Accessing Cylinder 8: The passenger-side rear plug (Cylinder 8) can be tight against the firewall and HVAC box. Use a combination of a swivel socket and a short extension to reach it safely without tilting the socket.

Known issues

While you don't have to worry about the infamous two-piece plug breakage seen on older Ford 3-valves, the GM Gen IV V8 architecture has its own quirks to watch out for.

• Cracked Porcelain: Because the coil brackets and exhaust manifolds are close to the plugs, it is very easy to accidentally put lateral pressure on your spark plug socket while turning your ratchet. This will crack the ceramic porcelain of the new plug. A cracked plug will immediately cause an ignition misfire, often accompanied by a ticking sound as the spark arcs to the engine block. Always ensure your extension is perfectly straight in line with the plug hole.
• Heat Shield Cuts: The metal heat shields surrounding the spark plug boots have incredibly sharp edges. Wear gloves, or you'll likely walk away with a few knuckle slices when pulling the plug wires off.

Need plugs replaced? Find a shop on Repairius.