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Best Spark Plugs for 4.0 Jeep


A jeep 4.0 comes equipped with a durable spark plug. But, you must have the electrical device examined by a mechanic after driving for approx. 30,000 miles. Choosing one of the best spark plugs for 4.0 jeep helps a lot. It can perform two basic tasks. One of them is sparking the mixture of fuel and air. Another one is dissipating heat from the combustion chamber.

Here are the top best spark plug for 4.0 jeep:

1. Bosch9656 Double Iridium OE Replacement OE Spark Plug:

This Bosch spark plug is the best one in this list due to its extraordinary features. It comes with a durable build quality at a reasonable price. What I liked the most is it comes with a 4 times longer life than other spark plugs

This product has a laser-welded type tapered ground electrode, which is great because it boosts the performance. Another great feature is its ultra-fine wire design. It can help you to carry the spark plug to a long distance.  


I admire its capability to boost the performance in your engine. This spark plug is designed to deliver high performance and longevity. Moreover, it comes with a ground electrode inlay and a double Iridium firing pin. Both of them are responsible for making this spark plug durable. That would be really useful when you want to try out an alternative of standard copper plugs. Another feature I liked is the ribbed insulator design. It stops flashover.


  • Outstanding ignitability and performance
  • Extreme durability in any weather condition
  • Comes with corrosion protection
  • The nickel-plated shell for protection
  • No anti-sieze
  • Affordable price


  • The gap portion comes with the cheap quality of metal
  • Needs more time for installation 
  • Mis-fire issue takes place occasionally 

2. Autolite XP985 Iridium XP Spark Plug, Pack of 1 

When it comes to performance upgrade for a 4.0 jeep, this Autolite spark plug is great. This spark plug come with0.6mm finewire center electrode. It is made up of iridium-enhanced platinum alloy. It provides a great performance boost in the ignition.  Another good feature is it comes with the V-trimmed type platinum sidewire technology. It stops corrosion. As a result, this spark plug guarantees long-lasting use. 


I really appreciate the OE equivalent design. It is designed to make sure this plug works for every engine.  To provide long life, the manufacturer designs these plugs with almost no gap erosion. A multi-rib insulator is available. It decreases the risk of flashover. 

What I liked the most is its necked-down style center electrode. It fires quickly, without any mess, and with less voltage. Hence, the ignition process is always easy and quick. This also helps to improve the fuel economy of the engine. The built-in resistor decreases radio frequency interference. Also, it reduces electrode erosion.


  • Focused ignition for efficient performance
  • Reduced gap erosion and fewer misfires 
  • Cheaper than service from a mechanic
  • Full copper core electrode offers high performance in all conditions
  • Easy to install


  • Does not improve mileage
  • No protective cover included

3: E3 Spark Plugs E3.58 Automotive Spark Plug (1) 

This automotive spark plug is designed to provide optimal performance. It can be used for a wide range of applications. I liked its ability to increase the efficiency of the engine and reduce fuel consumption.  Furthermore, this plug improves hydrocarbon emissions. It may be a good choice for those who want to effectively enhance the performance of 4.0 jeep. 

This spark plug comes with the DiamondFIRE ground electrode, which is secure to the shell using 3 legs.  It provides efficient heat transfer. Moreover, it boosts turbulence within the cylinder.


Another good feature is the excellent durability.  This plug is designed with cold heat ranges to allow performance changes. The yttrium-enhanced alloy is available. This is useful for a reduction in side wire temperature. As a result, there will be less pre-ignition.

With the help of this E3.58 spark plug, there will be an improvement in engine power output. Moreover, there will be a reduction in carbon monoxide emissions from the engine of 4.0 jeep. What I liked the most is this plug helps your 4.0 jeep to run efficiently with the latest technologies. The pack includes this plug, a 14 mm thread, a 0.75-inch thread reach plug along with gasket seat


  • Increases fuel efficiency up to 5%
  • Reduces emission of hydrocarbon
  • Complete combustion leads to more power and consistency
  • No loss of heat during the process
  • Enhances fuel mileage


  • May cause the engine to stall
  • Do not operate well in 6 cylinder jeeps

You can choose more:

Jeep Wrangler Grand Cherokee 4.0L 

NGK V-Power Spark Plugs for 1997-2006 Jeep TJ 4.0L L6

Champion RC12LYC (412) Copper Plus Replacement Spark Plug

Things To Look for Best Spark Plugs for 4.0 Jeep:

The important considerations help anyone to easily choose a suitable spark plug for 4.0 jeep. Let’s look at the things to consider:

1) Ignition efficiency:

The key purpose behind the use of a spark plug for a 4.0 jeep is to ignite the engine. This is why the ignition efficiency is a very important consideration. The feature to consider for this is the electrode gap affects the intensity of the sparking process. As a result, it decides the combustion level of the mixture of air and fuel. Hence, it is easy to understand that you need to buy a spark plug with high efficiency.  

Generally, the electrode gap is mentioned in millimeters. Furthermore, the performance of the engine depends greatly on the electrode gap measures.

Those spark plugs with a wide electrode gap offer a clean burning advantage. On the other hand, those spark plugs with narrow or small electrode gaps do not offer the above benefit. Hence, the ignition efficiency will be less.

2) Time for heating:

The decent quality spark plugs come with less time for heating. The heat rating is useful to determine this factor. Basically, the heat rating is defined as the range of temperatures within which that plug works smoothly. The number shows the score of heat rating. If it’s important for you to find a plug that works better in colder temperatures then go for the one with a higher heat rating.

Generally, the spark plugs with low heat ratings are recognized as hot-type plugs. They are usually suitable for light-duty vehicles. In such plugs, the firing end turns hot rapidly and also provides a bigger surface area to warm gases. On the other hand, those spark plugs equipped with a high rating come with firing ends that take more time to heat up. They are typically referred to as cold-type plugs.

3) Protection:

The protection features may be good choices for use in all weather conditions. In some spark plugs, you may find a nickel-plated shell. It protects against most external factors like extreme heat, rain, and other damage. Moreover, it is good to go for a spark plug with a corrosion resistance feature. It ensures durability for years. Some spark plugs guarantee no misfiring issues

4) Types of spark plugs:

The spark plugs for 4.0 jeep largely differ based on their material construction. In most cases, the materials can be any one from copper, platinum, and iridium.

The copper spark plugs are equipped with a durable core of copper. Moreover, a dense coating of nickel alloy is available. This might be a good choice for those who have older 4.0 jeep models with a low-voltage type ignition system.

The platinum spark plugs are more durable than those made up of copper. Moreover, the hardness of the platinum allows the metal to resist the high temperature of the engine. These plugs can check the pollution and accumulation of residues.

The iridium spark plugs are well-known for durability. They need fewer voltages for making sparks.

Read more: Best Sound System for Jeep Wrangler


From the discussion above, the winner is Bosch9656 Double Iridium spark plug.  It provides high-performance in terms of ignition. Also, durability is high. The great features like shell protection and corrosion are not found in the other two spark plugs. Also, it is more efficient in terms of the ignition and combustion process. This product fulfills all the necessary features and expectations of the customers for 4.0 jeep. 

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