2020 Ram 3500 Spark Plug Specs & Replacement Guide

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2020 Ram 3500 is not just about getting the engine to run; it's about optimizing performance, fuel efficiency, and longevity. The "right" plug encompasses several critical factors:

• Heat Range: This refers to the plug's ability to dissipate heat from the combustion chamber. A plug that's "too hot" (dissipates heat slowly) can lead to pre-ignition and detonation, severely damaging your engine. A plug that's "too cold" (dissipates heat too quickly) can cause carbon fouling. OEM plugs are meticulously engineered with the correct heat range for your specific engine.
• Electrode Metal: Modern spark plugs utilize various precious metals for their electrodes to enhance durability and extend service intervals:
  • Iridium: This is the most common precious metal used in modern, long-life spark plugs due to its extreme hardness and high melting point. Iridium plugs offer superior wear resistance and a very fine electrode tip, concentrating the spark for more efficient combustion. The 6.4L Hemi engines typically specify iridium-tipped plugs, offering extended replacement intervals.
  • Platinum: Platinum plugs are also durable and offer extended life compared to traditional copper plugs. They are often found in OEM applications but are gradually being superseded by iridium.
  • Copper: While copper has excellent electrical conductivity, it's a relatively soft metal. Copper spark plugs have thicker electrodes and a shorter lifespan, requiring more frequent replacement. They are rarely specified for modern engines like those found in the 2020 Ram 3500.

Using a plug with the wrong heat range or electrode material can lead to misfires, reduced power, decreased fuel economy, and potentially expensive engine damage.

How to gap a spark plug

Even though many modern spark plugs are "pre-gapped" from the factory, it is always recommended to double-check the gap before installation, especially for engines with precise ignition timing. For your 2020 Ram 3500 6.4L Hemi, the specified gap is 0.044 inches (1.1 mm).

1. Obtain a Gap Tool: Use a wire-style or coin-style spark plug gap tool. Blade-style feeler gauges can sometimes damage the delicate electrode tip of iridium or platinum plugs.
2. Check the Gap: Carefully slide the appropriate wire or coin gauge between the center and ground electrodes. There should be a slight drag.
3. Adjust (if necessary): If the gap is too small, gently pry the ground electrode only open using the adjustment tool on your gapping device. If the gap is too wide, carefully tap the ground electrode on a hard, non-marring surface (like a wooden block) to close it slightly. Never bend the center electrode. Be extremely careful with iridium and platinum plugs, as their fine electrodes are fragile.
4. Re-check and Verify: Re-check the gap to ensure it matches the specification.

Replacement procedure tips

Replacing spark plugs on your 2020 Ram 3500 6.4L Hemi is a manageable DIY task, but precision is key.

• Coil-on-Plug (COP) Removal: The 6.4L Hemi uses a coil-on-plug ignition system. Each spark plug has its own ignition coil directly mounted on top. To access the spark plugs, you'll need to carefully disconnect the electrical connector from each coil and then remove the coil mounting bolt (usually a 10mm or 8mm). Gently twist and pull to remove the coil from the spark plug well. Avoid yanking on the wires.
• Anti-Seize Debate: There is ongoing debate regarding the use of anti-seize on spark plug threads. Most modern spark plugs feature a special coating on the threads that acts as an anti-seize. Applying additional anti-seize can alter the torque readings, potentially leading to over-tightening and damage to the cylinder head threads. Most spark plug manufacturers, including NGK, recommend against using anti-seize unless explicitly stated by the vehicle manufacturer. For the 6.4L Hemi, it's generally recommended to install spark plugs dry unless the manufacturer specifies otherwise, relying on the plug's inherent coating.
• Dielectric Grease on Boots: Apply a thin film of dielectric grease inside the spark plug boot (the end that connects to the spark plug). This helps lubricate the boot for easy installation and removal, seals against moisture, and prevents voltage leaks, ensuring proper electrical connection.
• Torque Wrench is Crucial: Always use a calibrated torque wrench to tighten spark plugs to the specified 13 lb-ft (17.5 Nm). Under-tightening can lead to combustion gas leaks and overheating. Over-tightening can damage the spark plug, cylinder head threads, and even crack the porcelain insulator.
• Clean the Area: Before removing the old plugs, use an air compressor or vacuum to clear any debris from around the spark plug wells. This prevents dirt and grime from falling into the combustion chamber when the old plugs are removed.
• One at a Time: It's often best to replace one spark plug at a time to prevent mixing up ignition coils or having an open cylinder head port for too long.

Known issues

Fortunately, the 6.4L Hemi engine in the 2020 Ram 3500 doesn't have widespread, notorious spark plug replacement issues like the broken two-piece plugs found in some older Ford 3-valve engines or the ionization-sensing coil problems of certain GM 5.3L engines. However, always exercise caution to prevent:

• Cross-threading: Ensure the new spark plug starts easily by hand. If it doesn't thread smoothly, stop and re-align. Cross-threading aluminum cylinder heads is an expensive mistake.
• Over-tightening: As mentioned, over-tightening can strip threads or crack the plug insulator, leading to misfires.
• Damaging the Ceramic Insulator: Be careful not to bump or drop spark plugs, as this can crack the ceramic insulator, leading to an immediate misfire.

Need plugs replaced? Find a shop on Repairius.