2020 Ram 2500 Spark Plug Type, Gap & Torque Specs

As an ASE-certified master technician, I’ve worked on countless heavy-duty trucks. If you own a 2020 Ram 2500, you likely rely on it for serious towing and hauling. While the 6.7L Cummins diesel option doesn't use spark plugs, the mighty 6.4L HEMI V8 gas engine certainly does. Keeping this engine firing perfectly is critical to maintaining its impressive payload and towing capacities.

Here is everything you need to know about replacing the spark plugs on your 2020 Ram 2500 6.4L HEMI V8.

Quick reference

Why the right plug matters

Choosing the correct spark plug is more than just making sure the threads fit. The modern 6.4L HEMI is a high-compression, heavy-duty workhorse that demands specific heat ranges and electrode metals.

The heat range determines how quickly the spark plug transfers heat away from the firing tip into the cylinder head. A plug that is too hot can cause pre-ignition and engine knock, while a plug that is too cold will foul out with carbon deposits.

Furthermore, modern engines like the 6.4L require iridium spark plugs. Iridium is significantly harder and more durable than platinum or traditional copper. While copper conducts electricity exceptionally well, it wears out quickly (often in under 30,000 miles). Iridium allows for a precise, ultra-fine wire center electrode that reduces the voltage required to spark, ensures a more complete burn, and easily lasts for the manufacturer’s 100,000-mile interval.

How to gap a spark plug

Even if your new iridium spark plugs are advertised as "pre-gapped," a master tech never installs a plug without verifying the gap first. Shipping and handling can easily bump the ground electrode, altering the gap.

For the 2020 Ram 2500 6.4L, you are looking for a gap of 0.043 inches (1.1 mm).

1. Use the right tool: Do not use the old-school coin-style gappers on iridium plugs; dragging them across the tip can easily snap the fragile iridium wire. Use a wire-type feeler gauge.
2. Check the gap: Slide the 0.043-inch wire between the center and ground electrode. It should pass through with a slight "drag."
3. Adjust if necessary: If the gap is too tight or too loose, use the bending tool on your gauge to carefully bend the ground electrode. Never pry against the center iridium electrode itself.

Replacement procedure tips

Working on the 6.4L HEMI in a heavy-duty truck chassis presents a few unique challenges. Here are a few tips to make the job go smoothly:

• Double the Plugs: The most important thing to know is that the 6.4L HEMI uses a twin-spark system. This means there are two spark plugs per cylinder, for a total of 16 spark plugs. Make sure you order enough!
• Coil-on-Plug Setup: The 6.4L utilizes an individual ignition coil pack mounted directly over the primary spark plug, with a short wire leading to the secondary plug on the same cylinder. Disconnect the electrical connectors carefully, as the plastic locking tabs become brittle from engine heat.
• The Anti-Seize Debate: Most modern OEM and premium aftermarket plugs (like NGK and Champion) feature a special zinc or nickel plating on the threads designed to prevent seizing in aluminum cylinder heads. Therefore, adding traditional liquid anti-seize is not recommended, as it acts as a lubricant and can cause you to over-torque and damage the threads.
• Dielectric Grease: Always apply a small dab of dielectric grease to the inside of the ignition coil boots before reinstalling them. This prevents moisture intrusion, prevents voltage leaks, and makes removing the boots much easier the next time around.

Known issues

While the 6.4L HEMI doesn't suffer from the catastrophic two-piece spark plug breakage seen in older Ford 3-valve engines, there are still things to watch out for.

Because of the twin-plug design, accessing the rearward spark plugs on the passenger side (cylinders 6 and 8) can be incredibly tight against the firewall and brake booster area. You will need a good assortment of universal joints (swivels) and various lengths of extensions to get the socket squarely onto the plug. If the socket is tilted during removal or installation, you risk cracking the porcelain insulator, which will result in an immediate and severe engine misfire. Take your time, clear any wiring harnesses out of your way, and ensure your socket is perfectly straight.

Need plugs replaced? Find a shop on Repairius.