NGK Spark Plugs - how to decode the letter & numbering system #1453 (2023)


Ever wondered what the number & letter code means on the side of an NGK spark plug? Well, finally, they caught my attention after all these years so I did a little research to find out more...

In this video I run through how to decipher the Spark Plug code - for example, a BPR8ES? What does it mean? Well, you may be surprised to know that each of the characters has a specific meaning & here's how to decode it...

I have really only brushed the surface on the NGK coding but I'm hoping this video helps give you the basics so you'll know how to decode your own spark plugs.

Here's the link to NGK's 2015 Motorcycle Spark Plug catalogue - lots of really useful info & it includes the decoding table I used in the video:

Andy Mechanic


Now then, crew and welcome back to the Andy mechanic YouTube channel now I've been working with spark plugs for many many years and I've still never got around to learning what all the numbers and letters mean on the.

Why I use ng case map looks so how to decipher the code.

You know BP our 60s or whatever.

It is.

What does that really mean, because each letter and each number does have a very significant meaning, and sometimes you know you need a spark plug for your car.

That's gone, there's a non resistor type or you might have to have all of the soot, that's a resistor type, and you want to make sure that the guys selling them over the counter is giving you the right ones.

So, a bit of research and I found online on the NGK spark plug website a really cool little table to help you to you know decipher that code and I thought I'd.

Do a few of a few of the spark plugs I've got kicking around the workshop with you to give you an idea of how to use this chart.

Hopefully, it's going to be helpful to a few and I'm sure there'll be a lots of comments on this down the bottom.

So if you read those as well, you know he'll, give you more information, I'm sure about these different types of spark plugs and why they all vary a little bit for each application and there's a lot more spark plugs out there now than there ever used to be because there's so many specialist applications, so I thought the first one that I'd pick up is and they're all that my spark plugs draw.

Is this one here? Look it's a CR 6h s, a I, hope to then go.

Oh I care.

I know the six is a heat range, but that's pretty much all I know.

Oh, it's got an hour in it as well, which means it's a resistor, but let's do this properly.

So we know what it all means right: let's head down to the bench actually I'm, just thinking it before I started to film using the sheet.

You know on the bench which you can probably hardly read.

So hey I've got some screen capture software, so I'll use that on the laptop and we'll go through a few different plugs got quite a selection here, so we've got a there's, no unlock another one, so I'll read them out as I'm going through the screen capture.

You know on the laptop and I'll talk you through how to work at each one, and there aren't there's, there's a few exceptions to the rule as well.

I've noticed, but this is, you know, a journey that our learning curve that I'm really keen to get my head round, because you know I deal with spam, plugs on a regular basis and it's it'd be good to be able to interpret and have a good idea of what those numbers and letters mean all right.

It's going to get my laptop right, so the first plug is: was it a CR? 6H s a so? What does that mean? Okay? Well, the first letter can be a B or a C or a D and so on, and we look down this table here and C tells us that it's a 10 millimeter thread.

It's got a one.

Millimeter pitch and the socket size to fit that span plug should be 16 millimeters.

Well, that was easy enough.

Okay! Well, the next letter is an R.

Well, I know that is aa stands for a resistor type spark plug, and it could be any of these here.

Look so put em for compact L for short type P for protected center, electrode insulator.

Obviously after resistor you for surface or semi surface discharge and as ed inductive suppressor I've, never seen one with the Z.

Hmm, okay, what's next? Well, it's a number and it's a number six, and now it's got to do with the heat range.

Most people know the heat range.

One thing to bear in mind is the lower the number, the hotter, the plug temperature and the higher the number.

The cooler is very important not to get that mixed up as Benjamin found out what this DT hold the piston poor life.


Now the next letter is a H, so we need to look down here for H and that tells us the length of the plug the threads that go into the cylinder.

How long those threads are.

Now the next letter, as it is on here is an S.

The S stands for nickel non v, grooved center electrode, so it's nickel plated and the last number we've got all the last letter is an A and that a stands for a special designing, see down here.

Look a B, D, etc special designs.

So that's very specific to the application.

Well, that's that one isn't it wasn't too difficult, but this table is really helpful to try and work these out.


So let's just choose another one right: it's how about CPR 7 EI, - 9 that sounds complicated right, so log, so starting off again see what we've already done C before so that's 10 your thread, 1 mil pitch 16 mil socket size.

Now the P stands for a protected center, electrode insulator.

Really so a little look, that's the spark plug okay! Well, I! Don't know, I can't see any kind of additional protection.

It looks like a normal spark up to me, but it is quite long.

Isn't it on the threads so I'll come to that in a minute.

Okay, so P covers the protected center, electrode insulator and then we've got the old R.

So it's also got the R, which means it's a resistor type of spark plug.

So this one is a slightly cooler spark plug than the previous one.

This is a number seven and then we've got an e, so the e stands for the thread reach of 19 millimeters and to confirm the thread.

Reach is this length here from from there right down to here, so that, in this case, is about 19 millimeters yeah there to there right what else for God's okay.

So it's got an a on the end, so that means it's a special design again and then it's got a dash and a number nine well.

This example appears got an 11 on the end, so we'll follow that little line down, and that tells us that's.

If it's got a nine, it's already got a preset plug gap of 0.9 millimeters.

Now that might not necessarily be correct for your application, but it means it's quite at the factory with a preset little gap.

So this plug gap here between the two electrodes is 0.9.

Millimeters, just there look yeah easy and you can check it with a feeler gauge.

That's not hot! That's not putting my videos.

Ok, let's do one more for a third spark plug then, just for an example: let's go for the CR 9 ii model.

I suppose right.

So that's what it looks like again.

Quite a small thread size so thread size.

C again, we've got the 10 millimeter diameter one will pet the pitch and a 16 mil socket size.


The next one is the our circle resistor again and the 9 is the heat range.

This plug is quite a bit cooler than the previous ones have been looking at and it's got an e on the end, which means it's thread.

Reach is 19 mil, so that was actually quite an easy spark plug to do.

Excellent and you'll need to set the plug gap yourself, because it's not preset at the factory, okay, spat bugs all over the place.

Now, let's do one more before our voyage to death.

Every guard says this is a dr 8 e a and it's a used one, excellent okay, the 8 EA, sir D, will give us a 12 millimeter thread diameter.

So it's a bit bigger than that than the last one.

So 12 mil thread diameter and it's got a pitch of 1.25 millimeters and the socket size to go on here is an 18 millimeter socket and you should always use a proper spark plug socket because it's got the rubber sheath to hold it in place.

Okay, what else we got? So it's a our is the next letter.

So it's again it's a resistor type.

Look like most plugs are these days and it's number 8 on the heat range.

So it's somewhere by in the middle, really isn't it and E, which means again.

It's got a 19 mil thread reach across here down into the head and last one is a for Apple, and that means it's of a special design.

Yeah, pretty easy! Isn't it so there you go, got spark plugs all of our workshop.

Now they were tied it required, but that little chart there was really really helpful and what I'll do is I'll put a link to to where I got that from off the internet bit further down.

So you can actually download that chart yourself and give you somewhere safe because it's actually very informative.

There was a couple of things that I couldn't work out.

How to decipher that's gonna, be working, progress, I think I had one plug, which was a what was it was.

It was a D DCP, so somebody can tell us what that means: yeah that one there I think it was DCP r8e now, obviously, the r8 is easy and the DS easy, but the CP so needs to do with ISO standard says here.

If it was a if it was a BCP, not a DCP, the height from the gasket.

The top terminal is fifty point.

Five millimeters on a BK type spark plug mmm, which is 2.5 millimeters shorter than a BCP type.

That's a note.

Alright, so BCP will be 53 millimeters but looks of it anyway.

Yeah well, good I'm sure you know still learning okay.

Well, if you found this video helpful, why not click on the subscribe button? You'll see little gear icon turn up, click on the gear icon and then you can tick.

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Alright, crew! Well, until next time, I'll see you around Cheers Oh.

What else.


NGK Spark Plugs - how to decode the letter & numbering system #1453? ›

The heat rating is a measure of the amount of heat dissipation. The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of each NGK spark plug is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type.

What do the numbers on NGK plugs mean? ›

The heat rating is a measure of the amount of heat dissipation. The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of each NGK spark plug is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type.

What do the letter on a spark plug mean? ›

The letters refer to the center electrode material, projection dimension and ground material.

What is the letter R represents in a spark plug? ›

The “R” indicates a resistor type spark plug. Resistor type spark plugs reduce the amount of radio frequency interference (rfi) that can cause ignition misfires and static on the radio, if so equipped.

How do you read spark plug specs? ›

The stock number is a random 3-, 4- or 5-digit number and has no relation to heat range or plug type. An example is: DPR5EA-9; 2887. DPR5EA-9 is the part number and 2887 is the stock number. The exception to this is racing plugs.

What is a plug number? ›

Definition. The most basic definition of a plug may be "a placeholder number which is used in an overall cost or budget estimate until a more accurate figure can be obtained".

What is the difference between NGK iridium and platinum spark plugs? ›

Iridium is said to be six times harder and eight times stronger than platinum with a 700° higher melting point. Iridium spark plugs have extremely fine electrodes while retaining excellent wear characteristics. Thanks to its strength, iridium spark plugs can last up to 25% longer than comparable platinum spark plugs.

How do you know which spark plug is which? ›

The different types of spark plugs can seem overwhelming at first, but the simple way to find out what kind of spark plug you need is by checking your owner's manual. The manual will specify the right plugs for your vehicle.

Are NGK spark plugs pre gapped? ›

While most NGK spark plugs are pre-gapped, there are occasions when the gap requires adjustment. Care must be taken to avoid bending or breaking off the fine-wire electrodes. NGK recommends a round wire-style or pin gauge gap tool to measure the gap.

Are NGK spark plugs iridium? ›

NGK builds two types of iridium spark plugs: OE Iridium and Iridium IX®. Every plug in the Laser Series was designed for an OEM application. All dual precious metal plugs are designed to provide maximum longevity.

What is the difference between NGK resistor and non resistor plugs? ›

Since resistor type plugs actually “resist” some of the spark energy, non-resistor type plugs actually deliver a more powerful spark. It is for this reason that most racing plugs are non-resistor types. However, in most automotive applications, a resistor plug is required for proper vehicle operation.

What is the hotter plug number for NGK? ›

NGK plugs are colder the higher the number, hotter the lower the number. Starting with part # BKR6E-11 (heat range 6), a colder plug would # BKR7E-11 (heat range 7), a hotter plug would be # BKR5E-11 (heat range 5).

What is the spark plug gap on NGK R BR8ES? ›

The gap specification for the BR8ES spark plug is . 020".

What is the meaning of BPR6ES in NGK? ›

So again, in the case of BPR6ES, the '6' indicates it is suitable for mid range heat. After the number, the next letter or letters identify the reach of the spark plug. The reach is distance between the point at which it runs out of thread at the metal shell and the ground electrode at the end of the spark plug.

What should NGK spark plug settings be? ›

NGK doesn't recommend adjusting the plug gap more than . 008" in either direction. Beyond that slight adjustment, the ground electrode and center electrode won't align properly, hindering spark plug performance and drastically reducing plug life.

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