2025 Ford F-250 Super Duty — Spark Plug Type & Gap

When you rely on a 2025 Ford F-250 Super Duty to haul heavy loads, tow massive trailers, and idle on job sites, your ignition system is constantly put to the test. Ford’s modern gas powerplants—the 6.8L Boss V8 and the 7.3L "Godzilla" V8—demand top-tier ignition performance to maintain power and efficiency. As an ASE-certified master technician, I’m here to guide you through the exact spark plug specifications, gaps, and procedures for your Super Duty.

(Note: The 6.7L Power Stroke is a diesel engine and does not use spark plugs.)

Quick reference

Why the right plug matters

Choosing the correct spark plug is critical, especially in heavy-duty applications. The engine's computer precisely calculates ignition timing based on the specified heat range of the OEM plug. Installing a plug that runs too hot can lead to pre-ignition and catastrophic engine damage under heavy towing loads, while a plug that runs too cold will foul out prematurely.

Electrode material is just as important. The 2025 F-250 gas engines require Iridium or advanced Ruthenium spark plugs. While traditional copper plugs offer excellent conductivity, they wear out in a fraction of the time. Platinum offers better longevity, but Iridium is the gold standard for high-compression, heavy-duty truck engines. Iridium's extreme melting point ensures the electrode maintains its sharp edge, providing a consistent, concentrated spark for up to 100,000 miles.

How to gap a spark plug

Even though modern iridium spark plugs come pre-gapped from the factory, an ASE technician will always verify the gap before installation. Shipping drops can easily bend the ground strap.

1. Use a wire-style gauge: A coin-style gauge can easily snap the brittle iridium center electrode. Slide the correct size wire gauge between the center electrode and the ground strap. It should have a slight "drag."
2. Make adjustments carefully: If the gap is too tight, use the bending tool on your spark plug gauge to gently bend the ground strap away from the center electrode. Never pry against the center electrode itself.
3. Verify: Re-check with your gauge until you hit the precise 0.049 to 0.053-inch target.

Replacement procedure tips

Ford's modern pushrod V8s use a Coil-On-Plug (COP) ignition system, meaning there is an individual ignition coil sitting directly on top of each spark plug, eliminating the old-school distributor and spark plug wires.

• Coil-on-plug removal: Start by disconnecting the negative battery terminal. Remove the 8mm retaining bolts holding the ignition coils. Carefully pull the coil straight up. If the rubber boot is stuck, gently twist back and forth while pulling.
• The anti-seize debate: Modern Motorcraft and NGK spark plugs feature a specialized trivalent metal plating on the threads. Because of this, you should not use anti-seize on the threads. Adding liquid or paste lubricant alters the friction coefficient, making it incredibly easy to over-torque the plug and damage the aluminum cylinder head. Install them dry.
• Dielectric grease: Always apply a small dab of dielectric grease to the inside tip of the coil boot before reinstalling. This prevents voltage leaks, keeps moisture out, and ensures the boot won't bake onto the ceramic insulator over the next 100,000 miles.

Known issues

Many truck owners have nightmare memories of the older Ford 5.4L 3-valve V8 engines, which were infamous for 2-piece spark plugs that would separate and leave broken plug shells seized in the cylinder head, or earlier 2-valve engines that blew plugs out of the head entirely due to limited thread engagement.

You can breathe a sigh of relief with the 2025 F-250. Ford engineered the 6.8L and 7.3L V8s with robust, standard 14mm spark plug threads. The cracked porcelain and broken shell issues of the early 2000s are a thing of the past. The only "issue" to watch for on these modern engines is heat degradation of the coil boots nearest to the exhaust manifolds. If you are doing a 100,000-mile plug service, it is highly recommended to replace the rubber coil boots and springs simultaneously to prevent misfires under load.

Need plugs replaced? Find a shop on Repairius.