Resistor Vs. Non-Resistor Spark Plugs: Which Is Better?

Many drivers are asking which is better, a resistor spark plugs or non-resistor spark plugs. Resistor-type spark plugs combine an internal resistor to subdue the noise of the ignition produced during sparking when you are turning your vehicle on. The noise caused by the ignition can either be an RFI or a radio frequency interference or an EMI or electromagnetic interference. 

Both of these noises can disrupt electronic communication signals. It will affect the performance of the sound system and the cellular phones. A two-way radio can also be affected, and the engine management systems too. 

So now, let us talk all about the differences between the resistor spark plugs and the non-resistor spark plugs. So here we go.

Resistor Vs. Non-Resistor Spark Plugs

What Is The Difference Between A Resistor And Non-Resistor Spark Plugs?

Some people are curious about the differences between resistor spark plugs and non resistor spark plugs. If you choose a resistor spark plug, it will not give a hotter spark. Its natural state limits its current in the circuit, and it will drop its voltage into the plug. 

If you choose a cooler one, you can try a lower voltage spark. A resistor wire is made for radio suppression of the noise. The resistor plugs will raise the voltage that is needed so that the gap can be jumped. 

So you will raise the amount of energy that is imparted in the spark. So using a resistor plug can raise the voltage to the point that it can already create an insulation failure in the older coils. So now, let us discuss the differences between a resistor and a non-resistor spark plug.

1. Delivery Of More Spark

The first difference is what delivers the most spark. It is essential for a spark plug to deliver more spark because the spark plugs are the ones that ignite the engine from starting. The non-resistor type plugs are known to deliver a more powerful spark rather than the resistor type. 

The resistor type is actually resisting some of that spark energy. This is also the reason why those racing plugs are non-resistor types.

2. Electromagnetic Interference

The second difference is about the electromagnetic interference. The resistor spark plugs are primarily recommended in any type of vehicle, any vehicle using a board computer system that will monitor and control the engine’s performance. The reason behind this is because the resistor spark plugs are reducing electromagnetic interference. 

It is also recommended on any vehicle that has some other onboard electronic system. These systems are engine management computers, two-way radios, GPS systems, or whatever is recommended by the manufacturer. 

It is also said that if you use a non-resistor plug in some specific applications, it will cause the engine to have some harmful side effects.

3.  Radio Interference

The third difference is the radio interference. People say that you can have no benefit from a non-resistor spark plug in terms of radio interference. However, if you install a non-resistor plug, it can create a more unwanted interference from the radio (EMI).

Which Spark Plug Is Better – Resistor Or Non-Resistor?

The answer varies for every person. For some people, there is no benefit in a non-resistor spark plug. The modern-day ignition coils will make a sufficient voltage. 

They said that if you install a non-resistor plug, you are creating a more unwanted radio interference (EMI). This is because if you use a non-resistor plug, you will significantly increase the voltage and the current across the ground. 

If you also remove a resistor out of a plug, you will also have a significant increase. If you use a non-resistor spark, it will increase the voltage at the end of the spark plug.


In summary, resistor spark plugs and non-resistor spark plugs have been debated over the years, of which one is the better choice. The choice differs for every person. 

Every person has their say on the matter. However, the list of the differences above will give you an idea of how they are different from each other.

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Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more