What Glow Plug to Use with Different Nitro [Explained]

Using glow plugs on RC engines is the norm for all RC enthusiasts. It enhances the performance and makes the experience more fun. But choosing the proper glow plug for your RC vehicle can be a tricky one to handle.

So, what glow plug to use with different nitro?

You first need to understand why with different nitro percentages, you need to change your glow plug specification. Then going through how to select the proper glow plug as well as knowing how to install a nitro glow plug properly. Along the way, you also can understand more about the fuel mixture, size-types used for different temperatures, and so on.

Loving the preview? Let’s get straight into the details to know more!

Why Glow Plugs Change with Different Nitro Percentage?

Glow plugs used in RC nitro engines have different sizes, variations depending on the temperature and condition. This is a big aspect of RC cars. But one with great interesting combinations and mathematics. 

Normally, it’s easier and better to use spark plus as we use in car engines. But in the RC world, spark lugs are more complicated than using glow plugs. 

Why are glow plugs used instead of spark plugs?

Glow plugs are used in RC car engines for their ease of usage. Also, there are some key factors too. Which are,

  • No electrical system required
  • Simplistic function
  • Less weight
  • Reliability
  • Cost

Glow plugs don’t need any radiator, no electrical system. That means there’s no need for any battery, alternator, or any kind of wiring system within the RC engine. This saves your form a lot of cost and hassle. 

As well as makes the build simple, easy to repair, and durable for offroad use.

Now, let’s talk about the measuring requirements. That’ll help you to choose the particular nitro glow plug for your engine. 

Basically, there isn’t any universal formula to glow plug variation and numbering. Rather it’s varied within brands and product lines.

But a general rule is that the glow plug size is determined by the size of your RC nitro engine and the type of fuel it’s using. If you don’t find a compatible fuel then you easily make your own fuel.

Smaller engines need hotter glow plugs, while larger engines need cooler glow plugs. Engines that run fuel containing a high percentage of nitro favor the cooler plugs as well, while those that run on less nitro prefer hotter plugs. 

So, the general formula would be-

  • Small engine = Hotter plug
  • Large engine = Colder plug
  • High-nitro fuel = Colder plug
  • Low-nitro fuel = Hotter plug

This is the basic rule you have to maintain to choose your glow plugs.

How to Select the Proper Glow Plug Based on Nitro Percentage?

Selecting the proper glow plug for your engine is crucial. Otherwise, the wrong glow plug can damage your engine and become a hazard for anyone around your RC vehicle. 

You will know about what sized engine you are using. According to the diameter of your engine block, you can choose various RC glow plugs depending on your need.

Are all RC glow plugs the Same?

The simple answer would be, no. There are two types of glow plugs you can use for your RC vehicle. The standard type and the turbo plug type. These are the popular and most used glow plug types in RC builds.

A standard glow plug is used in the usual RC engines we see. You can identify the plug just by seeing its flat tip and copper washer fitting. 

These are the most basic and the most used glow plug for RC engines. They are reliable and durable. As well as easy to replace and cheaper to buy.

Then there are the turbo glow plugs. These glow plugs have a narrower end to disperse the fuel mixture. It works just like a turbo in a road vehicle. They concentrate more fuel mixture and deliver it to the engine. 

This lets the RC car produce more power and better performance for a short period of time. As these aren’t that reliable. They also cost a lot.

Now knowing the types of RC glow plugs, there are various different sizes of glow plugs you can find in the market. But getting the right sized one is dependent on what your engine needs and whether you need hot or cool temperature glow plugs and the type you need.

Cold to Hot Temperature

MediumNo. 10No.8No. 7No. 6

Depending on your nitro engine requirements, you’ll need to choose the right glow plugs. And then, you’ll need to check the RC glow plugs.

What Glow Plug to Use with 20% Nitro

To use 20% nitro mix on your RC engine, you’ll need to choose a glow plug accordingly. The problem is choosing the right nitro plug. Various manufacturers have their own plug sizes and names. This is because there’s no universal measuring method for RC glow plugs. 

Rather, it’s determined by which manufacturer makes the better quality glow plug for that particular size. In case of mixing 20% nitro, the McCoy #8 glow plug. They make the best one for 20% nitro mixing values. In the case of budget options, we’ll recommend the best within the categories.

What Glow Plug To Use With 25% Nitro

For 25% nitro mix, the best option would be the HPI Power Plug #1503 Medium Cold R4 Platinum/Iridium Glow Plug. This glow plug is the best one to use for 25% nitro mix. You can use this glow plug for .28 nitro engine as well. This makes it a versatile product to procure.

What Glow Plug To Use With 16% Nitro

A fuel mix with 16% nitro needs a hotter glow plug. For a nitro mix that is lower than 20%, you’ll need to use hotter glow plugs. For that, you can use quite a lot of glow plug variants. These could be,

You can also use these glow plug for .21 nitro engine. The lower concentration of nitro makes it a versatile situation. You can use various hot glow plugs. 

How do you check RC glow plugs?

Now before installing the glow plugs, you’ll need to check the glow plugs if they are all in good condition or not. To check them, you’ll need to use a glow plug igniter to check if they’ll work perfectly. 

How do I know if my glow plug igniter is working?

Using a glow plug igniter you’ll need to check your glow plugs for defects or issues. A glow plug igniter is basically a charged light. Using the igniter, you can see the glow plugs condition by the color it shows on its injector end. 

If your glow plug igniter is emitting light and letting you check the glow plugs with ease, then the igniter is working well. If not, then there might be some problems with the power delivery or the light. You might need to use a new one.

Do I Have to Change the Glow Plug if I Change the Nitro Percentage?

It’s a rule of thumb to change your glow plugin in accordance with your engine specification and the nitro percentage of your fuel mixture. Because the percentage of nitro used in the fuel mixture decides what type of nitro glow plugs you’ll need to use on your engine.

Basically, the higher the nitro percentage, the colder the glow plugs need to be. And if the nitro percentage is lower, then you’ll need hotter glow plugs.

This is because the ignition rate of the fuel mixture depends on the nitro percentage. If it’s high, then you’ll need low-temperature glow plugs and vice versa.

Also, the condition of your engine fuel flow, the weather make your fuel mixture to be adjusted. This also determines your glow plug use. We’ve mentioned the fuel mixture criteria below.

ConditionsGlow Plug ConditionFuel Mixture
Higher air temperatureHot PlugLean
Lower air temperatureCold PlugRich
Higher HumidityHot PlugLean
Lower HumidityCold PlugRich
Higher Barometric PressureCold PlugRich
Lower Barometric pressureHot PlugLean
Higher AltitudeHot PlugLean
Lower AltitudeCold PlugRich
Higher Nitro ContentCold PlugRich
Lower Nitro ContentHot PlugLean
Higher Oil ContentHot PlugLean
Lower Oil ContentCold PlugRich
Hotter Glow plug Cold PlugRich
Colder Glow PlugHot PlugLean

Here, lean fuel mixture means the nitro percentage is more than the fuel. Whereas, the rich mixture has a fuel mixture percentage higher than the nitro.

You’d also need to keep in mind the different percentages of nitro mix in your fuel. That also determines what type of glow plug you should use as well.

Generally, if the fuel mixture has 10-20% nitro, then you’ll need to use hot glow plugs. 20-30% mixture requires medium temperature glow plugs. And 30% or beyond nitro mix requires you to use cold glow plugs. 

How to Install Glow Plugs

Knowing which kind of glow plug you’ll need for your RC build, it’s time to know how to install it in your RC engine. The process is very simple and has a few steps along the way. Let’s get into it.

Firstly, using a glow plug igniter, you’ll need to check the glow plugs. As well as you go through the check, you’ll also need to ensure the nitro glow plugs are cleaned or not. If not, then you’ll need to clean the nitro glow plugs

How do you clean a nitro glow plug?

Firstly you have to check the glow plugs for any defects. If there aren’t any structural problems to it, then you can start cleaning them. To do that, you’ll need isopropyl alcohol and some thin quilled metal brushes. Simply dab the glow plug with the alcohol mixture and gently scrub the glow plug. The fuel and carbon residue will clear off after a few scrubs.

You can use a mini hand drill to attach the metal brush for easy and fast cleaning. Here are some of the best mini hand drills in the market.

You can use these products and get the best performance for your cleanup job. As well as on various other usages you may find.

After doing that, use a glow plug igniter and see if the glow plug is okay or not. If it’s okay, then you can start to install the glow plugs to your nitro engine.

Installation Process

Installing the glow plugs to your nitro engine is a fairly simple task if you have the right tools for it. You’ll need a special Allen wrench to install the glow plug on your engine.

Before installing you first have to insert the copper washer into your glow plug. This is an important step to follow. 

After you’re done with that step, take your Allen wrench and install the glow plug to your nitro engine at an angle. 

This will prevent the copper washer from falling off. You won’t need to screw it very tightly, rather install it with even pressure. 

And that’s it! That’s how you install the glow plug to your nitro RC engine. 


What’s the difference between N3 and N4 glow plugs?

The difference between N3 and N4 glow plugs. N3 is used for lower nitro fuels (below 10%). While the N4 is used for medium fuels (10-15%). The flow rate differentiates between these two types of glow plugs

How do you know if your RC glow plugs are bad?

You can test the glow plug on a driver to see if it’s good or bad. If the RC car starts and runs just fine without the glow plug being changed then you know that it was bad. And if your car isn’t running at all, then the issue might be more than your glow plug.

How do you test an RC igniter?

You can test your RC igniter by holding the base against the engine head while pushing the start button. It should glow brightly. You’re better off with a separate rechargeable ignitor rather than an integrated one. It’s easier to replace if damaged.


That’s all about what glow plug to use with different nitro. We’ve tried to explain all the possibilities for you to use glow plugs with different criteria. As well as the fuel mixture and installation process. 

We hope this elaborate explanation helps you to choose the correct glow plug for your RC vehicle. If you need to know more about these, a quick tip would be to contact an RC professional.

If you have any queries, let us know in the comments.

Have a great day.