2020 International MV – Spark Plug Type & Gap

Quick reference

Why the right plug matters

Spark plugs are a critical component in gasoline engines, igniting the air-fuel mixture in your engine's cylinders. Using the correct spark plug for your specific engine is paramount for optimal performance, fuel efficiency, and engine longevity. Factors such as heat range, electrode material (iridium, platinum, or copper), and correct gapping all play significant roles.

• Heat Range: The heat range refers to a spark plug's ability to dissipate heat from the combustion chamber. A plug that runs too hot can cause pre-ignition and detonation, leading to engine damage. A plug that runs too cold can foul, leading to misfires and poor performance. Each engine is designed for a specific heat range.

• Electrode Metal:

  • Iridium: iridium plugs are the most durable and offer the longest service life, often exceeding 100,000 miles. They feature a fine-wire iridium center electrode and often a platinum ground electrode, providing a strong, consistent spark.
  • Platinum: Platinum plugs offer good durability and a longer lifespan than copper, typically lasting 60,000 to 80,000 miles. They usually have a platinum disc on the center electrode.
  • Copper: Copper plugs have a large copper core electrode which makes them excellent at conducting electricity. However, the copper wears down more quickly, so they need to be replaced more frequently, typically every 20,000 to 30,000 miles. They are often used in older vehicles or high-performance applications where frequent replacement isn't an issue.

How to gap a spark plug

Gap is the distance between the center and ground electrodes of a spark plug. The correct gap ensures a strong, consistent spark. Too wide a gap can lead to misfires, while too narrow a gap can reduce spark energy.

1. Obtain the correct gap specification: Always refer to your vehicle's service manual or the spark plug manufacturer's specifications for the precise gap setting.
2. Use a gapping tool: A wire-type feeler gauge is recommended. Slide the correct size wire between the electrodes. It should slide with a slight drag.
3. Adjust carefully: If the gap needs adjustment, gently bend the ground electrode. Use the gapping tool's adjustment feature if available, or gently pry the electrode. Never bend the center electrode, as this can damage the plug.
4. Recheck: Always recheck the gap after adjustment to ensure accuracy.

Replacement procedure tips

While the International MV is a diesel truck, for gasoline engines, typical spark plug replacement involves these steps:

1. Gather your tools: You'll need a spark plug socket, ratchet, torque wrench, extensions, and potentially a universal joint.
2. Disconnect the battery: Always disconnect the negative battery terminal before working on electrical components.
3. Remove ignition coils or wires: Most modern engines use coil-on-plug (COP) ignition systems. Carefully disconnect the electrical connector and unbolt the coil. For older engines, detach spark plug wires by pulling on the boot, not the wire.
4. Clean around the plug: Before removing the old plug, use compressed air or a brush to clear any debris around the plug well to prevent it from falling into the combustion chamber.
5. Remove old plugs: Use your spark plug socket and ratchet to remove the old plugs. Be careful not to overtighten them during removal, which can strip the threads.
6. Anti-seize debate: There is ongoing debate about using anti-seize on spark plugs. Some manufacturers recommend against it, as it can alter the torque readings. Ford, for instance, specifically advises against it on many of their gasoline engines. Others still recommend a very thin layer. When in doubt, follow the spark plug manufacturer or vehicle manufacturer recommendations.
7. Dielectric grease on boots: Apply a small amount of dielectric grease inside the spark plug boots (where the boot connects to the ceramic insulator of the spark plug) to help prevent moisture intrusion and make future removal easier.
8. Install new plugs: Thread the new plugs in by hand first to avoid cross-threading. Once finger-tight, use a torque wrench to tighten them to the manufacturer's specified torque. Never overtighten.
9. Reinstall coils/wires: Reconnect the ignition coils or spark plug wires firmly.
10. Reconnect battery: Reconnect the negative battery terminal.

Known issues

The International MV primarily utilizes diesel engines, which operate on a compression-ignition principle and therefore do not have spark plugs. Issues found in gasoline engines, such as cracked porcelain on Ford 3-valve engines or broken plug shells, are not applicable to the International MV.

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