2020 Isuzu NQR Spark Plug Type, Gap & Torque Specs

As an ASE-certified master technician, I regularly field questions about medium-duty truck maintenance. If you are operating a gasoline-powered 2020 Isuzu NQR, you are likely running the robust General Motors 6.0L L96 V8 engine. While Isuzu is famous for its diesel powerplants, the GM-supplied 6.0L V8 gas engine is a popular, cost-effective alternative for fleet operators.

Keeping this workhorse running efficiently requires proper ignition maintenance. Below is your comprehensive guide to the spark plug specifications, gap sizes, torque settings, and replacement procedures for the 2020 Isuzu NQR gas model.

Quick Reference

*Note: ACDelco 41-162 is the updated Iridium replacement for the older 41-110 part number.

Why the Right Plug Matters

For a commercial vehicle like the Isuzu NQR, uptime is everything. The GM 6.0L V8 comes factory-equipped with iridium spark plugs.

Iridium vs. Platinum vs. Copper: Iridium is significantly harder and more durable than both platinum and traditional copper. Because it resists spark erosion and chemical wear so well, it maintains the proper gap over a much longer service life (typically nearly 100,000 miles). Downgrading to copper or platinum to save a few dollars will result in frequent misfires, poor fuel economy, and premature replacement intervals.

Furthermore, using the exact heat range specified by ACDelco or NGK ensures the plug tip stays hot enough to burn off carbon deposits, but cool enough to prevent pre-ignition (engine knock) while hauling heavy payloads.

How to Gap a Spark Plug

Most premium iridium spark plugs, including the ACDelco 41-162, come pre-gapped from the factory. However, shipping and handling can sometimes alter the gap. It is standard shop practice to verify the gap before installation.

1. Use the Right Tool: Use a wire-type gap gauge rather than a cheap coin-style gauge. Coin gauges can easily snap the fragile iridium center electrode.
2. Measure: Gently slide the 0.040-inch wire between the center and ground electrode. It should slide through with a slight "drag."
3. Adjust Carefully: If the gap is too tight, use the bending tool on the gauge to gently pull the ground strap back. Never pry against the center electrode!

Replacement Procedure Tips

The GM 6.0L V8 uses a coil-near-plug ignition system, meaning short spark plug wires connect the ignition coils (mounted on the valve covers) to the spark plugs.

• Removal: Always remove spark plugs when the engine is cold to prevent stripping the aluminum cylinder head threads. Twist the spark plug boot before pulling it off to avoid tearing the silicone rubber.
• The Anti-Seize Debate: ACDelco explicitly states do not use anti-seize on their modern spark plugs. The threads feature a special zinc-nickel plating that prevents corrosion. Adding anti-seize acts as a lubricant, making it incredibly easy to over-torque the plug and damage the cylinder head.
• Dielectric Grease: Apply a small dab of dielectric grease to the inside of the spark plug boot. This prevents moisture intrusion, stops high-voltage arcing, and makes the boots much easier to remove during the next service.

Known Issues

While you won't face the infamous two-piece spark plug breakage common to early Ford 3-valve engines, the GM 6.0L V8 does have a few quirks to watch out for during plug service:

• Spark Plug Wire Degradation: Because the exhaust manifolds run extremely hot on these medium-duty trucks, the short spark plug wires are subjected to intense thermal cycles. The internal carbon string can break down, causing high-rpm misfires even with new spark plugs. It is highly recommended to replace the plug wires concurrently with the spark plugs.
• Broken Exhaust Manifold Bolts: While replacing the plugs, take a moment to inspect the exhaust manifold bolts. The 6.0L V8 is notorious for snapping the rear-most manifold bolts flush with the cylinder head. If you hear a ticking noise on cold startup that fades as the engine warms, you likely have an exhaust leak.

Need plugs replaced? Find a shop on Repairius.