2025 Kenworth T680 Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2025 Kenworth T680 is crucial for optimal engine performance, fuel efficiency, and emissions control. Spark plugs are responsible for igniting the air-fuel mixture in your engine's cylinders, and an incorrect plug can lead to a host of problems.

Heat Range: Spark plugs are designed with a specific "heat range," which refers to their ability to dissipate heat. A plug that is too "cold" (dissipates too much heat) can lead to fouling, where carbon deposits build up on the plug, causing misfires. Conversely, a plug that is too "hot" can cause pre-ignition, leading to engine damage. The manufacturer specifies the correct heat range to ensure the plug operates within the optimal temperature window.

Electrode Metal: The material of the spark plug electrode significantly impacts its lifespan and performance.

• Copper: These are the most basic and least expensive plugs. They have a large copper core that conducts electricity well but wears relatively quickly. They are rarely used in modern heavy-duty diesel or natural gas engines due to their short lifespan.
• Platinum and Double Platinum: Platinum plugs offer improved durability over copper thanks to a platinum disc welded to the center electrode. Double platinum plugs have platinum on both the center and ground electrodes, extending their life even further. These are often used in distributor-less ignition systems where spark occurs on both the up and down strokes.
• Iridium: Iridium is an extremely hard and durable metal, allowing for very fine electrodes. This design concentrates the spark, improving ignition efficiency and extending the plug's life significantly. Iridium plugs are standard in many modern engines, including those found in the Kenworth T680 (if equipped with spark-ignition engines like natural gas variants), due to their longevity and performance benefits.

How to gap a spark plug

The spark plug gap is the distance between the center and ground electrodes. This gap is critical for a strong, consistent spark. An incorrect gap can lead to misfires, reduced fuel economy, and increased emissions.

To gap a spark plug:

1. Use the correct tool: Always use a wire-type spark plug gapping tool or a feeler gauge. Avoid coin-type gappers, as they can damage the fine electrodes of iridium or platinum plugs.
2. Measure the gap: Carefully slide the correct thickness wire or feeler gauge between the electrodes. It should have a slight drag.
3. Adjust if necessary: If the gap is too small, use the gapping tool to gently bend the ground electrode outwards. If the gap is too wide, carefully tap the ground electrode on a hard, flat surface to close it.
4. Re-check: Always re-check the gap after making adjustments.

Note: Many modern iridium and platinum spark plugs come pre-gapped from the factory and should generally not be gapped unless specifically instructed by the manufacturer, as improper gapping can damage the delicate electrodes.

Replacement procedure tips (Specific to heavy-duty natural gas/spark-ignition engines)

Replacing spark plugs on a heavy-duty truck like the Kenworth T680 (if equipped with a natural gas or spark-ignition engine) can be more involved than a passenger vehicle. Always consult the specific service manual for your engine for detailed instructions and safety precautions.

• Coil-on-plug (COP) Removal: Most modern heavy-duty spark-ignition engines utilize a coil-on-plug ignition system. Each spark plug has its own ignition coil directly mounted above it. To access the plugs, you