2018 International LT — Spark Plug Type, Gap & Torque

Quick reference

Note: All factory 2018 International LT powertrains are compression-ignition diesel engines. They do not use spark plugs, ignition coils, or distributors. Some variants employ an intake grid heater for cold starts; there are no glow plugs on these platforms either.

Why the right plug matters

On gasoline engines, choosing the correct spark plug heat range and electrode material (iridium vs. platinum vs. copper) is critical for stable ignition, longevity, and avoiding pre-ignition. However, your 2018 International LT’s A26 or Cummins X15 is a diesel. Diesels ignite fuel by heat of compression, not by a spark. As a result:

• There are no spark plugs to specify, gap, or torque.
• There are no compatible NGK, Denso, Motorcraft, or ACDelco spark plug part numbers for these engines.
• Routine ignition service items found on gas engines (plugs, wires, coils, distributors) are not applicable.

If you searched for “spark plug” specs because of a hard start or rough run, focus diagnostics on diesel-specific systems: battery/starting system performance, intake air heaters (grid heater), fuel quality and filtration, injector performance, high-pressure common-rail components, and aftertreatment/EGR-related concerns.

How to gap a spark plug

This section is provided for reference if you also maintain gasoline vehicles in your fleet. It does not apply to the 2018 International LT diesel engines described above.

• Use a wire-style gap gauge matched to the OEM specification for that gas engine. Do not rely on coin-style wedges that can distort fine-wire electrodes.
• Adjust by lightly bending the ground strap only. Never pry against the center electrode and never file iridium or platinum tips.
• Re-check the gap at several points to confirm parallel alignment of the electrodes.
• If the plug uses a precious-metal fine wire and arrives “pre-gapped,” still verify the gap—shipping can alter it.
• Always follow the torque spec for the specific gas engine’s cylinder head material and thread size.

Replacement procedure tips (what’s applicable on the LT)

Because there are no spark plugs on the 2018 International LT, there’s no coil-on-plug (COP) module or distributor to remove. Instead, consider these diesel-service tips that address the symptoms that often prompt “spark plug” questions:

• Cold-start aids: The A26 and X15 use intake air heating (grid heaters) rather than glow plugs. If you have extended cranking in cold weather, inspect the grid heater element, power feed, relay/solenoid, and control strategy. Verify battery state of health and cranking speed; slow cranking reduces compression heat.
• Fuel system: Hard starts and misfire-like symptoms typically trace to fuel quality, air intrusion, clogged filters, or injector performance. Follow OEM procedures for rail pressure tests and leak-down.
• Electrical connectors: High-current heater circuits and injector harnesses must be clean and tight. Use dielectric grease only on connector seals as specified—never on high-current terminals themselves.
• Fastener care: If you service intake components to access the grid heater or sensors, torque fasteners to spec and replace gaskets/O-rings as recommended to prevent boost leaks that mimic misfires.
• No anti-seize needed for “plugs”: Since there are no spark plugs, anti-seize guidance is moot here. For any threaded sensors you do service, use only the OEM-specified sealant or dry torque as directed.

Known issues (applicability)

• Ford 3-valve 2-piece spark plug breakage: Not applicable—your International LT has no spark plugs.
• GM 5.3L ionization-sensing coil concerns: Not applicable—no ignition coils on this platform.

If you are experiencing what feels like an ignition misfire, pursue diesel-specific diagnostics: charge-air leaks, EGR valve sticking, VGT turbo actuator issues, DPF regeneration status, and injector balance rates.

Need plugs replaced? Find a shop on Repairius.