2019 Ford F-350 Super Duty Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2019 Ford F-350 Super Duty is crucial for optimal engine performance, fuel efficiency, and longevity. Spark plugs are not "one size fits all" components; they are carefully engineered to meet the specific demands of each engine.

Heat Range: One of the most important specifications is the heat range. This refers to the plug's ability to dissipate heat from the combustion chamber. A "hotter" plug retains more heat, while a "colder" plug dissipates more. An incorrect heat range can lead to issues like pre-ignition, detonation, or excessive carbon buildup, all of which can damage your expensive engine.

Electrode Metal: The material of the center electrode significantly impacts the plug's lifespan and performance:

• Iridium: These are typically original equipment on modern vehicles like the F-350. Iridium is extremely hard and features a very fine tip, allowing for a concentrated, efficient spark. Iridium plugs offer the longest lifespan and best performance.
• Platinum: Platinum plugs are also durable, offering a longer lifespan than copper. They often feature a platinum pad on the center electrode.
• Copper: While excellent conductors, copper plugs have a shorter lifespan due to the softer metal. They are rarely found as OEM in modern engines but might be used in some performance applications where frequent replacement isn't an issue.

Using a plug with the wrong electrode material can reduce performance and require more frequent replacements, especially in engines designed for long-life iridium plugs.

How to gap a spark plug

While most modern iridium spark plugs come pre-gapped from the factory, it's always a good idea to verify the gap before installation, especially for the 6.2L and 7.3L gas engines in your F-350. Diesels, of course, do not have spark plugs.

1. Obtain a gap tool: Use a wire-type spark plug gapping tool or a feeler gauge. Avoid coin-style gapping tools, as they can damage the fine electrode of iridium plugs.
2. Measure the gap: Carefully slide the correct thickness wire or feeler gauge between the center and ground electrodes. It should slide in with a slight drag.
3. Adjust if necessary: If the gap is too small, gently pry the ground electrode very slightly with the adjustment tool on the gapper. If the gap is too large, gently tap the ground electrode on a firm, non-marring surface to close it. Be extremely careful not to touch or bend the delicate iridium center electrode.
4. Re-measure: Always re-measure after any adjustment to ensure accuracy.

Replacement procedure tips

Replacing spark plugs on your 2019 Ford F-350 Super Duty's gas engines (6.2L or 7.3L) involves working with a coil-on-plug (COP) ignition system.

• Coil-on-plug removal: Each spark plug has its own ignition coil mounted directly on top of it. Carefully disconnect the electrical connector by depressing the release tab and pulling. Then, using a gentle twisting and pulling motion, remove the coil from the spark plug. Avoid yanking on the wires.
• Anti-seize debate: There's ongoing discussion about using anti-seize on spark plug threads. Ford, like many manufacturers, often specifies not to use anti-seize on spark plugs with plated threads (which most modern plugs have). The plating acts as an anti-seize agent itself, and adding more can lead to over-torquing the plug due to reduced friction, potentially damaging the cylinder head threads. Refer to your owner's manual or a trusted Ford service manual for the definitive recommendation for your specific engine.
• Dielectric grease on boots: Before reinstalling the coil-on-plug boots, apply a small amount of dielectric grease inside the boot where it contacts the spark plug porcelain. This helps prevent moisture intrusion, insulates against voltage leaks, and makes future removal easier.
• Torque specs are critical: Always use a torque wrench to tighten the new spark plugs to the manufacturer's exact specifications (11 lb-ft / 15 Nm for these engines). Over-tightening can strip cylinder head threads or crack the spark plug porcelain, while under-tightening can lead to combustion gas leaks and overheating of the plug.

Known issues

Fortunately, the 6.2L V8 and the newer 7.3L "Godzilla" V8 engines in the 2019 F-350 do not suffer from the notorious spark plug issues that plagued some earlier Ford modular engines (like the 3-valve 5.4L and 6.8L engines with their two-piece spark plugs prone to breakage). These engines utilize more conventional and robust spark plug designs.

Need plugs replaced? Find a shop on Repairius.