What Spark Plug Do I Need For My Mustang?

Choosing a set of spark plugs for your Mustang can be a challenging task. There are a lot of different factors when considering the correct spark plug for your Mustangs engine. We will cover the basics of your Ignition System components and what you need to know when making your spark plug choice.

First off, we need to know what a spark plug is and what it does. A spark plug will be the final destination of your Mustang's ignition system. Whether an old-school distributor or a modern-day coil-on-plug setup, the spark plug will ignite the air/fuel mixture within the engine's cylinder. If your spark plugs are not working as intended, you can have severe driveability issues. This can include poor fuel mileage, misfires, difficult starting, and even catastrophic failure.

An engine's four main areas to operate correctly will be air, fuel, spark, and timing. When it comes to your spark plugs, there are also different areas of the plug you need to know for proper operation. Some of these will be your gap, heat range, and the material of the core/electrode of the plug.

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Spark Plug Gap

The plug gap is the air space between the electrode tip and your plug's ground strap. A more significant gap is more efficient as it provides a larger spark for a naturally aspirated Mustang. When adding a power adder like a supercharger or turbocharger, you want to close the gap to make the space smaller. The spark plug gap has to be reduced so the increased turbulence and pressure in the combustion chamber can ignite quicker and more intensely. When the spark plug gap remains larger under a boosted application, a misfire can result from the spark being blown out. You can always refer to your owner’s manual or underhood stickers for the proper gap your engine requires for factory applications. For modded Mustang applications, it is always best to consult your tuner. 

Spark Plug Heat Range

Spark plug heat range refers to the insulator (white ceramic) nose length where the ceramic meets the metal core to the firing tip. The insulator is typically the hottest part of the spark plug and is the main cause of pre-ignition and fouling. If the tip temperature is below 500 degrees celsius,  the insulator area surrounding the center electrode will not be hot enough to burn off carbon and combustion chamber deposits. These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature exceeds 850 degrees celsius, the spark plug will overheat, causing the center electrode to blister and the electrodes to melt. This may lead to pre-ignition and detonation issues in the engine. 

Considering the heat range of your plugs is an essential step for your engine build. If the wrong heat range is used, it can result in pre-ignition or detonation. This is especially common in forced induction applications. The heat range is ultimately the optimal operating temperature of the plug and resistance to heat. LMR recommends consulting your tuner for a high-performance application for the proper heat range needed for your build.

• What is the difference between changing the heat range on my spark plug?
  • In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber.

Spark Plug Core/Electrode Material

Different manufacturers use different materials when it comes to the core and the electrode of your spark plug. Typically, copper is used in most cases for core material. Due to its superior conductivity and overall longevity, this is the “go-to” choice for most automotive manufacturers. The outer area of the tip for your spark plug will be commonly referred to as the electrode. Some manufacturers use different materials here due to their added strength and resilience to wear from heightened cylinder pressures and heat. This can include metals like Iridium or Platinum; these metals are known for the amount of punishment they can handle over a stock or OEM plug.

Copper

• Lowest Cost 
• Highly conductive for improved spark voltage
• Not as long-lasting as platinum and iridium 
• Service interval for 20,000-30,000 miles

Platinum and Iridium

• Higher cost
• Less conductive than copper 
• Longer service lift, up to 100,000 miles

Projected Tip Vs. Non-Projected Tip  

Spark plug projection is simply the distance from the end of the metal shell (threaded section) to the center electrode's tip. From a performance standpoint, in high horsepower engines, the high heat created by the combustion process will heat the grounding strap to extremely hot temperatures. If this temperature gets the ground strap hot enough, the strap can be melted off the spark plug. On non-projected tip spark plugs, the grounding strap is naturally closer to the spark plug's threaded body, allowing the heat on the grounding strap to be dissipated to the spark plug threads and cylinder head, helping to prevent the grounding strap from melting off. 

• When to use projected tip vs. non-projected tip spark plugs?
  • The best answer to this is to ask your tuner. Your engine tuner will know what will work best in your engine. For example, we will use a 2011 Mustang 5.0 with forced induction at 6-10 psi. Depending on the timing and fuel used, this can be considered a fairly mild/street/low boost setup. If this 2011 Mustang were street-driven, most tuners would recommend a step or two colder spark plugs with a projected tip. If this 2011 Mustang was going to be running 10+ psi, high amounts of timing, and race fuel tune, a tuner may recommend a non-projected tip spark plug that is 1-2 steps cooler. 
• Non-projected tip spark plugs in a daily driven car.
  • One of the main reasons some tuners may not recommend non-projected tip spark plugs in a daily driven car is that their extremely low porcelain and ground strap can prevent the spark plug to self clean the spark plug. This is where the spark plug will get hot enough to clean the carbon off the spark plug from the combustion process under normal driving conditions. The spark plug can become fouled if the carbon is not cleaned during normal conditions.
• Does Projected and non-projected tip sparks affect the amount of heat a spark plug can remove?
  
  • Yes. A projected tip spark plug firing tip temperature will be 10-20 degrees celsius hotter than a non-projected tip spark plug. 

Spark Plug Reach

Spark plug reach is where the spark plug seats the cylinder head to the ends of the threads. This does not include the electrodes or any extensions. The cylinder head sets spark plug reach on the car. This will not come into play unless you change the cylinder heads to aftermarket units. Some aftermarket cylinder heads will require different spark plug reach.

Mustang Spark Plug comparison Charts

Use the following charts to compare some of your Mustang's most popular spark plugs. These are broken down by pushrod, modular motor, and Coyote motor spark plugs.

Related Ignition Items

As I mentioned earlier, the spark plug will be the final destination of your Mustang's ignition system. There will be many different areas of your Mustang’s engine that will affect the spark plug and how it operates. These can include some of the following parts below.

• Distributor
• Cap and Rotor
• Spark Plug Wires
• Ignition Coil
• Coil-on-Plug
• Battery

Using the information above, shop our spark plug selections below!

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