2018 International MV Spark Plug Type, Gap & Torque Specs

The 2018 International MV is a powerhouse medium-duty truck, renowned for its versatility in commercial fleets, utility work, and delivery services. As an ASE-certified master technician, one of the most common questions I get from fleet managers is about ignition maintenance on these chassis.

First, let's clear the air: the vast majority of 2018 International MV trucks are equipped with the Cummins B6.7 or L9 diesel engines. Because diesel engines rely on extreme compression to ignite fuel, they do not have spark plugs. However, International also offers Navistar/PSI (Power Solutions International) 8.8L V8 engines running on gasoline or propane (LPG) for fleets looking to avoid diesel emissions equipment. If your MV is equipped with the PSI 8.8L spark-ignited engine, this guide is for you.

Quick reference

Why the right plug matters

In a heavy-duty commercial application like the International MV, the PSI 8.8L V8 is under constant, grueling load. Using the correct spark plug is non-negotiable.

• Heat Range: Commercial trucks require spark plugs with a specific heat range to dissipate thermal energy effectively. A plug that is too hot can cause pre-ignition (detonation) under heavy hauling loads, destroying pistons. A plug that is too cold will foul out during prolonged idling.
• Electrode Metal: The PSI 8.8L thrives on Iridium spark plugs. While copper plugs are excellent conductors, they simply will not survive the high-temperature, high-load environment of a medium-duty truck for more than a few thousand miles. Iridium and Platinum plugs feature hardened tips that resist spark erosion, ensuring the gap stays consistent across thousands of engine hours.

How to gap a spark plug

Even if your premium Iridium spark plugs claim to be "pre-gapped" out of the box, you must verify the gap before installation. Shipping and handling can easily bend the ground strap.

1. Use a precise gauge tool: For modern iridium plugs, avoid the old-school sliding coin gauges, as they can snap the fragile iridium center electrode. Use a wire-type gap gauge or a specialized feeler gauge.
2. Measure the gap: Slide the 0.040" (1.0 mm) wire between the center and ground electrodes. It should slide through with a slight "drag."
3. A light bend: If the gap is too tight, use a proper gapping tool to gently bend the ground strap outward. Never pry against the center electrode! If the gap is too wide, gently tap the ground strap on a soft wooden workbench to close it.

Replacement procedure tips

Working on a medium-duty truck chassis requires attention to detail. Here are my top professional tips for servicing the ignition system on the PSI 8.8L V8:

• Coil-on-Plug Removal: This engine utilizes an individual ignition coil for each cylinder. When removing the coils, twist the boot gently before pulling upward. Heat cycling in commercial trucks can bake the rubber boots onto the spark plug porcelain. Tearing a boot means replacing the entire coil drop or boot assembly.
• The Anti-Seize Debate: Modern premium spark plugs (like NGK and ACDelco) feature a special trivalent metal plating on the threads that acts as a release agent. Adding traditional liquid anti-seize to these threads can cause you to over-torque the plug by as much as 20%, stretching the threads or cracking the cylinder head. Install them dry.
• Dielectric Grease: Always apply a small, pea-sized dab of dielectric grease to the inside tip of the new spark plug boot. This prevents moisture intrusion, stops voltage leaks, and ensures the boot won't fuse to the porcelain during the next 50,000 miles of service.

Known issues

While the PSI 8.8L is a robust engine based on proven heavy-duty V8 architecture, there are a few things to watch out for:

• Cracked Porcelain from Vibration: Medium-duty trucks ride rough. The extreme harmonic vibrations combined with the heat of the engine bay can sometimes lead to micro-fractures in the spark plug porcelain if the plugs were dropped before installation or torqued incorrectly. If you experience a random misfire under load, carefully inspect the porcelain for hairline cracks or carbon tracking.
• Industry Context: Fortunately, the PSI 8.8L does not suffer from the infamous 2-piece spark plug breakage seen in the older Ford 3-valve 5.4L/6.8L engines. The plugs in the International MV thread out conventionally. However, always remove spark plugs when the engine is cold to prevent pulling the aluminum threads out of the cylinder head.

Need plugs replaced? Find a shop on Repairius.