2021 Jeep Wrangler Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2021 Jeep Wrangler isn't just about getting an engine to start; it's crucial for optimal performance, fuel efficiency, and engine longevity. Modern engines, like those in your Wrangler, are designed with precise specifications, and the spark plugs are an integral part of that design.

Heat Range: Each engine requires a specific "heat range" for its spark plugs. This refers to the plug's ability to dissipate heat. A plug that's too "cold" (dissipates heat too quickly) can lead to fouling, while a plug that's too "hot" (dissipates heat too slowly) can cause pre-ignition and engine damage. The OEM-specified plugs have the ideal heat range for your Wrangler's engine.

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

• Iridium: These are the most common type for modern vehicles due to their exceptional durability and small electrode tip, which provides a strong, consistent spark. Iridium plugs typically last 100,000 miles or more, which is why they are often specified for factory-installed spark plugs in newer vehicles like the Wrangler.
• Platinum: Platinum plugs offer good durability, often lasting 60,000-100,000 miles. They are a step up from traditional copper plugs but generally less durable than iridium.
• Copper: While copper has excellent conductivity, it's a softer metal, so copper spark plugs wear out much faster, typically requiring replacement every 20,000-30,000 miles. You'll rarely find copper plugs as OEM for newer vehicles, but they can be used in older applications or for specific performance tunings where frequent replacement is acceptable.

How to gap a spark plug

While many modern iridium spark plugs come pre-gapped, it's always a good idea to double-check and adjust if necessary, especially with aftermarket plugs. However, be extremely careful when gapping iridium or platinum plugs, as their fine electrodes can be easily damaged.

To gap a spark plug, you'll need a spark plug gapping tool – either a wire-style gauge or a ramp-style gauge. For fine-wire iridium plugs, a wire-style gauge is preferred to avoid damaging the delicate tip.

1. Check the gap: Slide the correct size wire of your gauge between the center and ground electrodes. It should fit snugly with a slight drag.
2. Adjusting the gap: If the gap is too small, use the gapping tool to gently bend the ground electrode very slightly outwards. If the gap is too wide, gently tap the ground electrode on a soft, non-abrasive surface to close it. Never put pressure on the center electrode when gapping. Make small, incremental adjustments.

Replacement procedure tips

The 2021 Jeep Wrangler utilizes a coil-on-plug (COP) ignition system for both the 2.0L Hurricane I4 and 3.6L Pentastar V6 engines. This means each spark plug has its own ignition coil directly mounted on top of it, eliminating spark plug wires.

1. Coil-on-plug removal: Carefully disconnect the electrical connector from each ignition coil. Then, gently twist and pull upward on the coil to remove it from the spark plug. Avoid yanking on the wires.
2. Anti-seize debate: There's a long-standing debate about using anti-seize on spark plug threads. For modern spark plugs with nickel-plated shells, manufacturers like NGK and Denso generally advise against using anti-seize. The nickel plating provides adequate corrosion resistance and acts as a lubricant. Using anti-seize on these plugs can lead to over-torquing, potentially damaging the cylinder head or the spark plug itself, as anti-seize can alter the torque readings. Follow the spark plug manufacturer's recommendation.
3. Dielectric grease on boots: Applying a small amount of dielectric grease inside the ignition coil boot (where it contacts the ceramic of the spark plug) is a good practice. This helps to seal out moisture, prevents corrosion, and makes future removal easier.
4. Torque specs are critical: Always use a torque wrench to tighten the new spark plugs to the manufacturer-specified torque. Over-tightening can strip threads or crack the spark plug, while under-tightening can lead to poor electrical contact, combustion gas leakage, and the plug backing out.

Known issues

Fortunately, there are no widespread, specific "known issues" related to spark plugs on the 2021 Jeep Wrangler's 2.0L Hurricane I4 or 3.6L Pentastar V6 engines, such as the Ford 3-valve 2-piece plug breakage. Adhering to the recommended maintenance schedule and using the correct spark plugs and torque specifications will help ensure trouble-free operation.

Need plugs replaced? Find a shop on Repairius.