Best Spark Plugs For 4.0 Jeep – 2021 Buyers Guide

| Last Updated: December 14, 2021

Do you need to change your spark plugs and have no idea which are best for your 4.0?

We’ll cover the best reviewed options here that we’ve selected on a number of factors:

Comparison of the Best Spark Plugs For 4.0 Jeep

  • Featuring several anti-corrosion and anti-seizing properties
  • Core Material: Copper Core
  • Electrode Material: Nickel Alloy
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  • Allows you optimal heat range control
  • Core Material: Copper Core
  • Electrode Material: Centre Electrodes of Copper-Nickel Alloy
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  • Best for the Money
  • Core Material: Copper Core
  • Electrode Material: Nickel Centre Electrodes
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  • Highlighted by a 7 year manufacturer warranty
  • Core Material: Copper Core
  • Electrode Material: Iridium Electrodes
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  • With three legs for more efficient heat transfer
  • Core Material: Copper Core
  • Electrode Material: Nickel Alloy
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Factors to Consider Before Buying New Spark Plugs

Spark plugs are essential parts of your car’s ignition system. Without them, your car won’t go anywhere. Nowadays, there are a couple of options you can choose from when buying them. Make sure you know which are the best.

Know Your Specifications

Many things have changed since Robert Bosch created the first high-voltage spark plug, which was commercialized in 1901. The original design has been improved over the years. 

When spark plugs were first used in a car’s ignition system, there was only one type available. Because of the variety of options that we have today, it’s crucial to know which type best fits your car.

First, you should check what kind of spark plugs your car manufacturer installed originally. In case your car uses spark plugs with precious metals, it’s not recommended to downgrade them to cheaper materials. 

It would negatively affect your car’s performance in mileage and gas effectiveness. Check your car’s manual for more accurate information. 

Mind the Gap

The gap on a spark plug is the space between electrodes inside it. The smaller this gap is, the less efficient it tends to be. So, broader gaps usually mean more resistance. Those gaps can be adjusted manually, even if you aren’t a professional. 

With a simple tool called a spark plug gap gauge, it’s possible to measure and change it quickly.

Setting the proper gap for your plugs ensures better performance overall, gas management, and smoothness. 

A narrower gap can lead to weak sparks, while wider gaps may produce no spark at all. 

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Heat Range

Check the heat range of your plug before buying it. The heat range concerns the temperature at which a plug can work optimally. 

Different materials have different heat ranges. A plug should never get too hot, as high temperatures will cause malfunctions in the ignition, damaging the engine. Too cold plugs, on the other, can completely misfire.

That said, there are a few applications for hotter or colder plugs. Hot plugs can achieve a better fuel/air mixture and will burn better on oil-fueled engines. 

Cold plugs may be suitable for modified cars for performance, with turbochargers, high compression ratio, and so on. In normal driving conditions, it’s advisable to use the plug that your manufacturer recommends. 

Review of the Best 4.0 Jeep Spark Plugs

Before you get lost among so many options, check our quick reviews on the leading brands and plugs of the moment. In this section, you’ll read about their composition, particularities, advantages, and liabilities.

Best Overall

Sixity Auto NGK V-Power 4024180432

6 pc NGK V-Power Spark Plugs compatible with Jeep TJ 4.0L L6 1997-2006 Ignition Wire Secondary


Core Material: Copper Core

Electrode Material: Nickel Alloy

Electrode Style: V-Cut

Manufacturer Part#: 402418043

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This plug is designed for hassle-free domestic use. Moneywise, the benefits outweigh the price. Copper is a cheap and effective material for ignition systems, and this one is placed closer to the fuel mixture to ensure better combustion. 

Its copper core is very effective in dissipating heat. Its nickel alloy also represents an upgrade in comparison with OE standard nickel plugs. It’s interesting to notice how it’s popular with racers, although its warranty doesn’t cover this type of usage. 

Bottom Line

It’s perfectly fit for everyday usage of a regular car. In good conditions, this plug will rarely misfire or have flashovers. It also offers good durability, considering its stock price. Although its installation can be tricky, changing it with regularity is a pretty affordable way to keep your car running smoothly.


Insulation design prevents shorts

Provides excellent fuel management and mileage

Insulation system allows for quick dissipation of heat

Because its ignition is placed closer to the fuel mixture, it rarely misfires

It’s cost-effective. Considering its cost, it offers impressive benefits and superb quality




Champion Copper Plus 412

Champion Copper Plus 412 Spark Plug (Carton of 1) - RC12LYC


Core Material: Copper Core

Electrode Material: Centre Electrodes of Copper-Nickel Alloy

Electrode Style: Gasket

Manufacturer Part#: 412

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This plug makes use of a pretty clever combination of cheap materials to achieve superior performance. It also has a copper core, but its electrodes use a special copper-nickel alloy, bringing many benefits. This alloy presents better conductivity and corrosion resistance. 

The results are a greater life span and dependability. It enhances fuel performance through a better sparking system. Its gap size can vary quite a bit, although it’s usually pre-set at 0.035″. Always check your manual before carrying out any adjustments.

Bottom Line

This plug can be considered an upgrade over standard OE copper plugs. It uses the same materials but creates exclusive alloys. It offers superior ignition and better corrosion resistance. It’s recommended to replace it every 20,000 miles.


Provides better performance overall

Its copper core provides a long life span and heat control

It can be used in older vehicles manufactured before the 1980s

It’s cheap and cost-effective, as it uses less expensive materials

It has excellent fuel management, thanks to its sparking technology


Its exterior material isn’t very resistant and can wear out quicker

SBest for the Money


NGK (3459) ZFR5N V-Power Spark Plug, Pack of 1


Core Material: Copper Core

Electrode Material: Nickel Centre Electrodes

Electrode Style:  V-Grove

Manufacturer Part#: 723661

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This is another copper core and nickel electrodes spark plug. Although, this one is distinguishable by its V-cut, which gives sparks more room for expansion. The result is better fuel burning and economy, as well as lower emissions. 

It uses a unique trivalent metal plating, which is much more resistant to corrosion caused by chemical or electrical exposure. Its compliance with OE standards ensures a seamless replacement of your original plugs. 

If you want to keep its warranty, you should hire an authorized mechanic to install them for you. Otherwise, you may not be able to claim it if necessary.

Bottom Line

While using the same materials as standard plugs, this one stands out from the crowd by applying a V-groove. This simple solution can improve sparking reliability and better fuel burning. Its recommended mileage should be carefully observed since it tends to become brittle and crack over time.


Its V-cut provides better ignition

It has excellent emission control

Its exclusive design prevents flashovers

It’s effortless to install and has many models available

It’s very resistant to chemical and electrical damages over time


Some have experienced cracked porcelain

Editor’s Pick

Bosch 9656 Double Iridium

Bosch Automotive (9656) OE Fine Wire Double Iridium Spark Plug - Single


Core Material: Copper Core

Electrode Material: Iridium Electrodes

Electrode Style: Tapered

Manufacturer Part#: 9656-4PK

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This plug uses rare metals in its composition, with superb performance results. It lasts much longer than any regular plug: something between 80,000 and 120,000, with no sensible performance loss. 

It still uses a copper core, though. The iridium electrodes can stand a much wider heat range while avoiding pre-ignition. It comes pre-gapped from the factory and rarely needs any change. 

You should also be careful with the installation of this one. The warranty won’t cover any damages caused by unauthorized professionals.

Bottom Line

It uses noble metals in its composition, and the price says it all. It’s considerably more expensive than any copper-and-nickel spark plug. Yet, its top-quality construction can lead to a better economy down the road since it lasts much longer and improves performance.


Iridium provides better gas management

It’s pre-gapped, and typically, it doesn’t require further adjustments

Its copper core prevents pre-ignition and dissipates heat more efficiently

It requires a lower voltage to work, increasing the reliability of your spark

It has long durability, lasting between 80,000 and 120,000 miles, keeping its performance


It’s considerably more expensive than copper spark plugs, although it comes with many compensating features

Honorable Mention

E3 Spark Plugs E3.58

E3 Spark Plugs E3.58 Automotive Spark Plug, Pack of 1


Core Material: Copper Core

Electrode Material: Nickel Alloy

Electrode Style: Diamond-shaped

Manufacturer Part#: E3.58

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Here’s another copper and nickel alloy plug, although this one uses its alloy. This core’s shape is different; the diamond-shaped core provides more efficient sparks than regular copper ones. 

It comes pre-gapped from the factory, but it can be adjusted at your discretion. This nickel alloy results in more efficient combustion and an increase of 6% in power output. Despite not using any costly metal in its composition, this plug tends to be more expensive than those with the same materials.

Bottom Line

This plug delivers superior performance compared to similar ones. The diamond-shaped copper core is an exclusive feature. 

It allows for better projection of sparks, resulting in better combustion. This plug also has a much longer lifespan than other copper plugs: up to 100,000, compared with the common 30,000 miles standard. You may need special tools for installing it.


Great longevity

Can stand extreme situations, and it’s very resistant

Offers better combustion, thanks to its exclusive nickel alloy

Construction allows for better heat management, especially in the side wire


More expensive than typical copper options

Top Spark Plug Brands in the 4.0 Jeep Space

There are a couple of types of plugs you can choose from when you go shopping for your Jeep. In this section, you’ll read about some of the best options available.

NGK V-Power

One noticeable feature of this plug is its cost-effectiveness. It has superior performance and is compatible with vehicles from 1997 to 2006. 

This plug uses a V-Cut electrode, which provides better ignition. It’s also more resistant to corrosion. It follows OEM specifications. 

Bosch Double Iridium OE

This plug has a much longer life than the copper ones, plus better ignitability. In normal conditions, it provides seven years of good performance.

But, you may have to adjust the gap yourself. Those are more reliable overall. It’s compatible with vehicles from 2009 to 2020.

Autolite XP985 Iridium XP

It’s known for its greater resilience, good ignition, and structure. Its superior ignition is due to a platinum alloy combined in the iridium wire. It also comes with a motor sit and also offers a guarantee for seven years. Even so, they can be tricky to the gap. It’s compatible with a wide variety of vehicles: from 1983 to 2001.

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How Often to Change Spark Plugs in a 4.0 Jeep

It depends on the materials employed by your plugs. Generally, plugs can be conventional or long-life. Long-life ones are made of nobler materials, such as iridium and platinum, which are more resilient. Standard spark plugs should be changed every 30,000 miles

Long-life plugs typically last between 60,000 and 150,000, depending on the vehicle. It’ll also depend on the type of fuel you use. Low-quality fuels will wear your plugs out quicker. 

Since 2001, Jeep has changed the ignition system of its 4.0 line, like Wranglers, Cherokees and Grand Cherokees. They’ve changed from a distributor system to a distributorless one, which is more modern and of cheaper maintenance. 

You can tell what kind of system your car uses by checking if it has a spark coil rail. In case it does, your vehicle uses the distributorless system.

Watch out for signs of deterioration on your spark plugs. Worn-out plugs will have naturally bigger gaps. For this reason, it can misfire or waste fuel, and those symptoms will clearly show on your car’s performance. 

Some specialists suggest that plugs should be changed every 30,000 miles, whether they show signs of deterioration or not. 

Sixity Auto NGK V-Power 4024180432


After reading this guide, you should have a clearer picture of your options when buying a new spark plug. Your best choice will depend on what your needs are, and of course, your budget. 

Iridium plugs have many benefits, but your car can also do with more traditional materials like copper and nickel alloys. Just make sure you set the correct gap and follow the installation guidelines, so you won’t risk losing your plug’s warranty. 

Quick Summary – Best Spark Plugs For 4.0 Jeep

Before you head out, here’s a quick wrap-up of the best spark plugs for 4.0 Jeep:

  1.  Sixity Auto NGK V-Power 4024180432
  2.  Champion Copper Plus 412
  3.  NGK ZFR5N

People Also Ask

Make sure you use only the most appropriate parts for your car. Check your car’s manual for information before you go shopping. Using incorrect spark plugs can be costly and dangerous. If you still have doubts about your spark plugs, you can find further information in this section. 

Do High-End Spark Plugs Make a Difference?

Plugs made of noble metals can’t make your car perform better than it was initially intended. Still, they perform much better than those made of traditional materials and help to preserve your engine for longer. They’re more expensive than regular ones, but they need replacement less frequently. 

Can Spark Plugs Increase Horsepower?

They do increase horsepower, albeit slightly. An upgrade of your spark plugs can mean an increase of up to 2%. This belief is rooted in a theory that says that better plugs will produce more sparks and burn more fuel. Yet, new cars are designed to burn all the fuel regardless. 

What is the Spark Plug Gap for a 4.0 Jeep?

Many users prefer to set between 0.35 and 0.45 inches, but some prefer bigger gaps, depending on the ignition system. Those users maintain that bigger gaps lead to better combustion, provided the gap isn’t too big. Some materials may allow for greater gaps than others, like platinum, for instance. 

What Happens If a Spark Plug Gap is Too Big?

A wider gap means that the electric current has to travel further to generate a spark. Too wide gaps on the plugs can result in ignition malfunctions, such as weak sparks, misfiring, and engine hesitation. Ultimately, it shortens the plugs’ lifespan, leading to wet, black, and fouled plugs. 

What Are the Symptoms of Bad Spark Plugs?

Spark plugs need to be replaced regularly. Otherwise, they can damage your engine, waste your fuel, and lead to several other malfunctions. Here are the tell-tale signs your plugs need replacement: slow acceleration, bad fuel management, constant misfirings, and difficulty starting the engine. 

Do I Need to Replace All My Spark Plugs at the Same Time?

Yes, you should replace the whole set. Make sure you’re using the correct plug, or you may have problems down the road. Having your plugs with the same resistance and longevity will ensure more consistent performance. As you usually buy them as a set, it’s advisable to change them all at once.

Who Worked on This?



A master of organization, Brian helps keep everything running smoothly for Your Jeep Guide.

No Jeep yet but we’re working on that!



Cory loves his XJ and frequently thrashes it through the hills. He’s constantly fixing something.

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