2022 Ram 3500 Spark Plug Type & Gap Specs

As an ASE-certified master technician, I know that keeping a heavy-duty workhorse like the 2022 Ram 3500 running at peak performance requires strict adherence to maintenance schedules. For the gas-powered 2022 Ram 3500 models, spark plugs are the literal spark of life for your engine.

Before we dive into the specifics, it is vital to note that the 2022 Ram 3500 comes with two main engine types: the 6.4L HEMI V8 (gasoline) and the 6.7L Cummins Turbo Diesel. Diesel engines rely on high compression to ignite fuel and do not have spark plugs. If you drive a Cummins, you are off the hook for this maintenance item. If you drive the 6.4L HEMI V8, keep reading—your engine requires exactly 16 spark plugs (two per cylinder) to operate efficiently.

Quick reference

Why the right plug matters

Choosing the correct spark plug is crucial for optimal engine efficiency, longevity, and emissions control. The 6.4L HEMI V8 utilizes a dual-spark plug ignition system to burn the air-fuel mixture more completely, increasing power and reducing emissions.

Using the correct heat range prevents pre-ignition (pinging) if the plug is too hot, or fouling if the plug is too cold. Furthermore, electrode metal matters immensely. The OEM standard for this engine is an iridium-tipped spark plug. Iridium is significantly harder and more durable than traditional copper or even platinum, allowing the plugs to reliably withstand the intense pressures of the HEMI combustion chamber for up to 100,000 miles. Never downgrade to standard copper plugs on an engine designed for iridium; you will end up replacing them in a fraction of the time and risk misfires.

How to gap a spark plug

Even though modern premium iridium plugs usually come pre-gapped from the factory, an ASE-certified technician will always verify the gap before installation. A plug dropped in shipping can easily have its gap closed.

1. Use the right tool: Use a wire-style gap gauge or a feeler gauge. Avoid coin-style gauges on iridium plugs, as they can easily snap the ultra-fine center electrode.
2. Measure: Gently slide the 0.043 in (1.1 mm) wire gauge between the center and ground electrode. There should be a slight drag.
3. Adjust: If the gap is too tight, use the gapping tool's adjustment notch to gently bend the ground strap outward. Never pry against the delicate iridium center electrode. If the gap is too wide, tap the ground strap lightly on a soft wooden workbench to close it.

Replacement procedure tips

Replacing 16 spark plugs on a heavy-duty truck engine can be a daunting task, but following best practices ensures a clean job.

• Coil-on-Plug (COP) System: The 6.4L HEMI utilizes a coil-on-plug setup with dual-lead ignition coils. You will need to carefully unplug the electrical connectors and remove the retaining bolts to pull the coils and boots out. Keep them organized.
• The Anti-Seize Debate: Most modern OEM and NGK iridium plugs feature a specialized trivalent metal plating that acts as a release agent. Using liquid anti-seize alters the friction coefficient of the threads, often leading to over-torquing and potential cylinder head damage. Install them dry unless the service manual specifically demands otherwise.
• Dielectric Grease: Apply a pea-sized amount of dielectric grease inside the tip of the ignition coil boots before reinstalling. This prevents moisture intrusion, stops high-voltage tracking, and ensures the rubber boots don't weld themselves to the ceramic ribs of your new plugs.
• Blow out the wells: Always use compressed air to blow out the spark plug wells before removing the old plugs. Heavy-duty trucks collect a lot of dirt, and you do not want debris falling into the cylinders.

Known issues

While the 6.4L HEMI doesn't suffer from the infamous multi-piece plug breakage associated with older Ford 3-valve engines, its main hurdle is simply access and volume. Having 16 spark plugs means the rear cylinders closest to the firewall (Cylinders 7 and 8) require patience, a variety of locking extensions, and universal swivel joints to access safely. Take your time, ensure the socket is seated perfectly straight to avoid cracking the new porcelain, and hand-thread the new plugs to prevent cross-threading the aluminum cylinder heads.

Need plugs replaced? Find a shop on Repairius.