2020 Jeep Grand Cherokee Spark Plug Type & Gap Guide

As an ASE-certified master technician, I can tell you firsthand that keeping up with spark plug maintenance is one of the most cost-effective ways to ensure your 2020 Jeep Grand Cherokee runs flawlessly. Whether you have the reliable 3.6L Pentastar V6 or the powerhouse 5.7L HEMI V8, using the correct spark plug type, setting the right gap, and applying proper torque is absolutely essential for maximum fuel efficiency and engine longevity.

Below is your complete guide to replacing the spark plugs on your 2020 Jeep Grand Cherokee.

Quick reference

(Note: Always verify the exact part number with your vehicle’s VIN, especially if you have the 6.2L Trackhawk, which uses specialized colder heat-range plugs).

Why the right plug matters

Modern engines like the Pentastar and HEMI are highly sensitive to ignition system variations. The correct heat range dictates how well the plug transfers heat into the cylinder head. A plug that is too hot can cause pre-ignition (pinging) and engine damage, while a plug that is too cold will foul out prematurely.

Equally important is the electrode material. The 2020 Grand Cherokee utilizes iridium spark plugs from the factory. Iridium is significantly harder than platinum and copper, allowing for a much finer wire center electrode. This concentrates the spark for a highly efficient burn and resists wear, which is how these engines achieve a 100,000-mile replacement interval. Downgrading to copper or standard platinum will result in a weak spark and require replacement in a fraction of the time.

How to gap a spark plug

Even though premium iridium plugs usually come pre-gapped, you should always verify the gap before installation. Shipping and handling can occasionally bump the ground strap and close the gap.

1. Use the right tool: Avoid using traditional coin-style gap tools on iridium plugs, as sliding them can snap the brittle, fine-wire iridium tip. Instead, use a wire-style feeler gauge.
2. Measure: Gently slide the 0.043" (1.1mm) wire gauge between the center electrode and the ground strap. It should have a slight "drag" to it.
3. Adjust carefully: If the gap is too tight, use the bending notch on your gap tool to gently pull back on the ground strap. Never pry against the center iridium electrode.

Replacement procedure tips

Replacing plugs on the 2020 Grand Cherokee requires some specific knowledge depending on which engine sits under your hood.

• 3.6L Pentastar V6 Intake Removal: The driver-side cylinder bank on the V6 is buried underneath the upper intake manifold (plenum). You will have to remove this intake plenum to access the coils and plugs. When you do, always replace the intake manifold gaskets to prevent vacuum leaks and avoid throwing lean codes later.
• 5.7L HEMI Twin-Spark Design: The 5.7L HEMI V8 uses a coil-on-plug setup, but it utilizes a twin-spark design. That means there are two spark plugs per cylinder—16 plugs in total for the V8 engine! Plan your parts order and time accordingly.
• Anti-seize Debate: Mopar does not recommend using anti-seize on the plug threads for these engines. The OEM and premium aftermarket plugs feature a nickel-plated shell designed to prevent seizing. Adding anti-seize acts as a lubricant, which can easily lead to over-torquing the plug and stripping the aluminum cylinder head threads.
• Dielectric Grease: Always apply a small dab of dielectric grease to the inside of the coil boot before pressing it back onto the new plug. This prevents moisture intrusion and stops the rubber boot from baking onto the plug's porcelain insulator.

Known issues

While you won't face the notorious broken 2-piece spark plug shells found in older Ford 3-valve engines, the Jeep's coil-on-plug boots can become extremely brittle over 100,000 miles of heat cycling. If you are doing a high-mileage tune-up, it is highly recommended to replace the coil boots (or the entire ignition coils) alongside the spark plugs to prevent misfires.

Furthermore, exercise caution when removing the coils on the 3.6L Pentastar. The locking tabs on the electrical connectors become very fragile with age; use a gentle touch and a small pick to slide the red locking tabs back before depressing the release latch.

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