2025 Kenworth W900 Spark Plug Type & Gap

Quick reference

Why the right plug matters

While the Kenworth W900 is predominantly a diesel truck, and therefore does not utilize spark plugs, understanding spark plug technology is crucial for gasoline engines. The type of spark plug, its heat range, and the electrode material all play a significant role in engine performance, fuel efficiency, and longevity.

Heat Range: A spark plug's heat range refers to its ability to dissipate heat. A "cold" plug dissipates heat quickly, while a "hot" plug retains more heat. Using the correct heat range is essential to prevent pre-ignition (too hot) or fouling (too cold).

Electrode Metal:

• Iridium: Considered the best for performance and longevity. Iridium plugs offer superior durability and a finer electrode, leading to a more consistent spark and longer replacement intervals (often 100,000 miles or more).
• Platinum: A step up from copper, platinum plugs provide better durability and resistance to wear, with replacement intervals typically around 60,000 to 80,000 miles.
• Copper: The most basic and least expensive. Copper plugs have larger electrodes and shorter lifespans, usually requiring replacement every 30,000 miles. They are often found in older or high-performance engines that benefit from their superior conductivity.

How to gap a spark plug

While not applicable to your Kenworth W900, gapping a spark plug correctly is vital for gasoline engines. The gap setting determines the distance the spark must jump, directly impacting combustion efficiency. To gap a spark plug:

1. Use a wire gauge tool: These tools are specifically designed to measure the gap between the center and ground electrodes.
2. Measure carefully: Slide the appropriate wire gauge into the gap. It should fit snugly without forcing.
3. Adjust gently: If the gap is too small, use the gapping tool to gently bend the ground electrode outwards. If it's too wide, carefully tap the ground electrode on a hard, non-abrasive surface to close the gap. Never bend or pry on the center electrode.
4. Re-check: Always re-measure the gap after making adjustments.

Replacement procedure tips (for gasoline engines)

Although your Kenworth W900 does not have spark plugs, for gasoline engines, specific replacement tips can make the job easier and prevent damage:

• Coil-on-plug removal: Most modern engines use a coil-on-plug (COP) ignition system. Carefully disconnect the electrical connector and then pull straight up on the coil pack to remove it. Avoid prying.
• Anti-seize debate: There