2016 Peterbilt 579 Spark Plug: Type, Gap & Torque

Quick reference

Why the right plug matters

The 2016 Peterbilt 579, being a heavy-duty truck, predominantly uses diesel engines. Diesel engines do not use spark plugs for ignition; instead, they rely on compression ignition. Therefore, spark plug considerations like heat range, electrode material (iridium vs. platinum vs. copper), and gapping are not applicable to the main PACCAR MX-13 engine options.

While some specialized Peterbilt 579 configurations might exist with gasoline engines (e.g., for niche applications or aftermarket conversions), the vast majority of these trucks are equipped with diesel powertrains. If your 2016 Peterbilt 579 is indeed a gasoline-powered variant, it is crucial to consult your owner's manual or a certified Peterbilt service center to determine the correct spark plug specifications.

For general knowledge, and in the rare event of a gasoline engine in a Peterbilt 579, here's why the right spark plug matters for gasoline engines:

• Heat Range: Spark plugs are designed with a specific heat range, which refers to their ability to dissipate heat. A "hot" plug retains more heat, while a "cold" plug dissipates it quickly. Using the wrong heat range can lead to pre-ignition (too hot) or fouling (too cold), both of which can damage the engine.

• Electrode Metal:

  • Iridium and Platinum: These are premium materials known for their durability and long service life. They typically offer more consistent spark and better fuel efficiency over extended periods. Most modern engines, if gasoline, would specify iridium or platinum plugs.
  • Copper: While excellent conductors, copper plugs wear out faster and are usually found in older vehicles or specific high-performance applications where their superior conductivity is prioritized over longevity.

How to gap a spark plug

This section is generally not applicable to the 2016 Peterbilt 579 due to its diesel engine. However, for gasoline engines, proper gapping is crucial:

1. Consult specifications: Always refer to the manufacturer's specifications for the correct gap distance.
2. Use the correct tool: A wire-type spark plug gapping tool is recommended for accurate measurement and to prevent damage to the electrode. Avoid disc-style gap tools as they can widen the gap unevenly or damage delicate iridium/platinum electrodes.
3. Adjust carefully: If adjustment is needed, gently bend the ground electrode using the gapping tool. Never apply pressure to the center electrode.
4. Re-check: Always re-check the gap after adjustment to ensure it meets specifications.

Replacement procedure tips

Again, for the standard diesel PACCAR MX-13 engine in the 2016 Peterbilt 579, this section is not relevant as there are no spark plugs to replace. For a hypothetical gasoline engine, general tips would include:

• Coil-on-plug removal: Modern gasoline engines often use coil-on-plug ignition systems. Carefully disconnect the electrical connector and then unbolt and remove the ignition coil. Grasp the coil body, not the wires.
• Anti-seize debate: There are differing opinions on using anti-seize on spark plug threads. Some manufacturers advise against it, as it can alter torque readings and lead to over-tightening. Others suggest a tiny amount on threads for easier removal in aluminum heads. Always follow your engine manufacturer's recommendation.
• Dielectric grease on boots: Applying a small amount of dielectric grease inside the spark plug boot (the part that connects to the top of the spark plug) can help prevent moisture intrusion and make future removal easier.
• Cleanliness: Ensure the area around the spark plug is clean before removal to prevent dirt and debris from falling into the combustion chamber.

Known issues

There are no known issues related to spark plugs for the 2016 Peterbilt 579 PACCAR MX-13 diesel engine because it does not use spark plugs.

If, by some rare chance, your truck has a gasoline engine, then common issues with spark plugs in general gasoline engines can include:

• Cracked porcelain: This can lead to misfires and can be caused by improper installation or extreme thermal stress.
• Worn electrodes: Over time, the electrodes wear down, increasing the gap and leading to misfires and reduced fuel efficiency.
• Fouling: Oil, carbon, or fuel deposits can build up on the plug, preventing a strong spark.

Need plugs replaced? Find a shop on Repairius.