2016 Ram 2500 — Spark Plug Type, Gap & Torque Specs

Quick reference

Note: Never rely on generic part numbers. Mopar supersessions and VIN-specific plugs are common—confirm by VIN in the Mopar/NGK/Denso catalog or with a Ram dealer. The 5.7L and 6.4L HEMI each use 16 spark plugs (two per cylinder).

Why the right plug matters

• Heat range: Heavy towing, high loads, and extended idling demand the correct heat range to avoid fouling (too cold) or pre-ignition (too hot). Stick to the OE-specified heat range—HEMI chambers are sensitive to it.
• Electrode metal:
  • Copper/nickel: Excellent conductivity and OE feel, but shorter life—often serviced around 30,000 miles.
  • Platinum: Longer life, stable gap over time; good for extended intervals.
  • Iridium: Best longevity and stable spark under harsh duty cycles; often paired with 100,000-mile service intervals when specified by the manufacturer.
• Two-plug ignition (HEMI): Each cylinder fires two plugs to complete the burn. Running mismatched plugs or skipping the “second” plug will reduce performance and can set misfire codes.

How to gap a spark plug

1. Verify the spec: For most 2016 Ram 2500 HEMI engines, the target is 0.043 in (1.10 mm). Always confirm your exact spec by VIN.
2. Use a wire-loop gap gauge (not a coin wedge) for accuracy on fine-wire plugs.
3. Check gap on every new plug—shipping can alter it. Do not pry on the center electrode.
4. To adjust, apply a light bend to the ground strap only. For iridium/platinum fine-wire plugs, avoid filing and keep the strap square to the center electrode.
5. Recheck after adjustment and before installation.

Replacement procedure tips (5.7L & 6.4L HEMI)

• Two per cylinder: Both HEMIs use 16 plugs. Each cylinder has a coil pack with an integrated boot for one plug and a short secondary lead to the companion plug. Service one cylinder at a time to avoid crossing wires.
• Access & prep: Work on a cold engine. Blow debris from plug wells before removal. Disconnect the negative battery cable if desired for safety.
• Coil removal: Unplug the coil electrical connector, remove the retaining bolt, and lift the coil straight up. Note routing of the short plug wire to the second plug.
• Removal technique: Crack each plug loose, then back out slowly. If resistance is high, thread back in slightly and work it out in small steps. A dab of penetrating oil in the well can help with carbon-stuck plugs.
• Torque: Clean, dry threads only. Most modern nickel-plated plugs do not require anti-seize; using anti-seize can cause over-torque. If you choose to use it against manufacturer guidance, reduce torque by ~20%.
• Spec: Tighten to 13 lb-ft (18 Nm) on the HEMI aluminum heads. Use a 5/8-inch spark plug socket with extension and a torque wrench.
• Boots & seals: Apply a small amount of dielectric grease inside each boot to aid future service and prevent tracking. Ensure a positive “click/seal” on both plugs per cylinder.
• Final check: Clear any stored misfire codes, start the engine, and verify smooth idle. Recheck coil connectors and wire routing.

Distributor vs. coil-on-plug: Both HEMI gas engines use coil-on-plug (with a short secondary lead for the paired plug). There is no distributor.

Known issues

• Carbon-stuck plugs if service is delayed: Extended intervals on copper plugs can allow carbon to build and make removal difficult. Working stone-cold and using a controlled break-loosen-back-in method helps prevent broken porcelain.
• Crossed short leads: On HEMIs, mixing up the short plug wires per cylinder will create immediate misfires. Label before removal.
• Coil connector/boot wear: Age and heat can crack connectors and harden boots, leading to intermittent misfires under load.
• Aluminum head threads: Always start plugs by hand to avoid cross-threading. If resistance is felt early, stop, realign, and try again.

Issues not applicable here: The notorious Ford 3-valve 5.4L two-piece plug breakage does not apply to the Ram 2500 HEMI engines, and GM ion-sensing coil concerns are irrelevant to this platform. The 6.7L Cummins diesel uses glow plugs, not spark plugs.

Need plugs replaced? Find a shop on Repairius.