2015 Jeep Grand Cherokee Spark Plug Type & Gap Specifications

As an ASE-certified master technician, I can tell you that the 2015 Jeep Grand Cherokee is a phenomenal SUV, but its maintenance requires strict attention to detail—especially regarding the ignition system. Whether you are wrenching on the reliable 3.6L Pentastar V6 or unleashing the power of the 5.7L or 6.4L Hemi V8s, using the correct spark plugs, torquing them properly, and gapping them to spec is critical for optimal fuel economy, smooth idling, and full power delivery.

Below is your comprehensive guide to the spark plug specifications, replacement intervals, and service procedures for the 2015 Jeep Grand Cherokee.

Quick reference

(Note: The 3.0L EcoDiesel V6 utilizes glow plugs, not spark plugs, and is excluded from this chart. Note that the 5.7L and 6.4L V8 engines require 16 spark plugs—two per cylinder.)

Why the right plug matters

Choosing the correct spark plug involves more than just finding threads that fit; it is heavily dependent on electrode metallurgy and heat range.

• Electrode Metal: Modern engines like those in the 2015 Grand Cherokee are tuned specifically for the resistance and longevity of Iridium spark plugs. While older copper or single-platinum plugs were cheaper, they degrade rapidly under the high-energy demands of modern Coil-On-Plug (COP) ignition systems. Iridium center electrodes are highly resistant to spark erosion, which is exactly why Chrysler rates these intervals at 100,000 miles.
• Heat Range: The heat range dictates how fast the spark plug pulls heat away from the firing tip into the cylinder head. Using a hotter plug than specified can cause pre-ignition and catastrophic piston damage, whereas a colder plug will foul out with carbon deposits. Always stick to the OEM heat range unless the engine is heavily modified (e.g., forced induction).

How to gap a spark plug

Even if your premium iridium plugs are advertised as "pre-gapped," a master tech always verifies the gap before installation. Plugs can easily be dropped or mishandled during shipping.

1. Use the Right Tool: Use a wire-style gap gauge or a specialized feeler gauge. Avoid the cheap "coin-style" ramp gauges, as they can easily snap the brittle iridium center electrode.
2. Measure: Gently slide the 0.043-inch wire between the center and ground electrode. It should slide through with a slight "drag."
3. Adjust: If the gap is too tight, use the bending tool on your gauge to slightly bend the ground strap away from the center electrode. Never pry against the delicate iridium tip.

Replacement procedure tips

Working under the hood of the 2015 Grand Cherokee requires some specific techniques depending on your powerplant:

• 3.6L Pentastar Upper Plenum: To access the driver-side bank of spark plugs on the 3.6L V6, you must remove the upper intake manifold (plenum). Always replace the molded rubber intake gaskets when reinstalling the plenum to prevent vacuum leaks that will trigger a P0171 or P0174 lean code.
• The 16-Plug Hemi: Both the 5.7L and 6.4L V8s use a twin-spark system with Coil-On-Plug technology. You will be buying and installing 16 spark plugs. Take your time, as the rearmost plugs near the firewall can be a tight squeeze. A swivel spark plug socket and various locking extensions will be your best friends.
• The Anti-Seize Debate: Chrysler/Mopar explicitly advises against using anti-seize on the spark plug threads for these aluminum cylinder heads. Modern NGK and Mopar plugs feature a trivalent metal plating that acts as a release agent. Adding anti-seize alters the friction coefficient, making it incredibly easy to over-torque the plug and strip the aluminum threads.
• Dielectric Grease: Always apply a small dab of dielectric grease inside the tip of the coil boot. This prevents the rubber from fusing to the porcelain over the next 100,000 miles and blocks out moisture to prevent spark arc-over.

Known issues

While the 2015 Jeep Grand Cherokee does not suffer from the infamous broken 2-piece spark plug shell issue found in older Ford 3-valves, there are still pitfalls to avoid.

On the 3.6L Pentastar, the 10mm bolts holding the ignition coils to the plastic valve covers can bind. If you use an impact driver to zip them out, you risk stripping the plastic threaded inserts molded into the valve cover, requiring a complete valve cover replacement. Remove them carefully by hand. For the Hemi V8s, failure to torque the plugs correctly (13 lb-ft) is the number one cause of spontaneous misfires due to loss of ground or compression blowout.

Need plugs replaced? Find a shop on Repairius.