Spark plug socket sizes are the measurements of the sockets that fit over the spark plugs in your engine. These sizes vary with the type and model of your engine. They are usually measured in millimeters or inches, ranging from 8mm to 24mm.
Using the wrong socket size can strip or crack your spark plugs. It can cause engine misfires, poor fuel economy, or even total engine failure.
Imagine! You struggle with a stubborn spark plug for hours under the hood only to find that your socket doesn’t fit. The scenario can turn a simple maintenance task into a headache-inducing ordeal.
How do you know what size socket you need?
In the upcoming sections, I will explore the different spark plug socket sizes and their specific uses. I will also provide helpful tips to simplify the selection process. So, let’s go and find the best spark plug “socket size” for your CAR!
Understanding Spark Plugs
Spark plugs are small metal devices that screw into your engine’s cylinder head. They have two ELECTRODES.
- Centre Electrode
- Ground Electrode.
When electric current flows through these electrodes, a mini explosion in the cylinder sets off. This boom pushes the piston and starts the crankshaft moving. This process happens thousands of times per minute, generating the power your vehicle needs to zoom down the road!
The effectiveness and performance of your engine depend on the spark plugs. They need to produce a strong and consistent spark at the right time and temperature to ensure optimal combustion and prevent knocking or pre-ignition.
They must also withstand high pressure and heat and resist corrosion and fouling from carbon deposits or oil.
Different Types of Spark Plugs
Spark plugs are made of different materials. They can have copper, platinum, or iridium tips. Some have single electrodes, while others have multiple electrodes.
Let’s walk you through some typical spark plug varieties and how they differ.
1. Copper Spark Plugs
Copper spark plugs are the oldest kind of spark plugs. They have a copper centre and a nickel alloy covering on the electrodes. They are also known as ‘standard‘ or ‘conventional‘ spark plugs.
Pros
- They are cheap and widely available
- They have good conductivity and heat dissipation
- They work well with older engines that have low-voltage ignition systems
Cons
- They wear out quickly and need to be replaced more often
- They are prone to corrosion and fouling
- They cannot handle high temperatures or pressures
2. Platinum Spark Plugs
Platinum spark plugs are an upgrade from copper spark plugs. They have a platinum tip on the centre electrode, which reduces wear and improves durability. They are also known as ‘single platinum’ or ‘double platinum spark plugs’, depending on whether they have one or two platinum tips.
Pros
- They last longer than copper spark plugs and need less maintenance
- They have better resistance to corrosion and fouling
- They provide better fuel efficiency and performance
Cons
- They are more costly than copper spark plugs
- They have lower conductivity and heat dissipation than copper spark plugs
- They may not work well with some engines that require a hotter spark
3. Iridium Spark Plugs
Iridium spark plugs are the most advanced and high-priced spark plugs. They have an iridium tip on the centre electrode, which is harder and stronger than platinum. They also have a delicate wire design, which lowers the voltage required to make a spark. They are also known as ‘iridium IX’ or ‘iridium XP spark plugs’.
Pros
- They last longer than platinum or copper spark plugs and need minimal maintenance.
- They have excellent resistance to corrosion and fouling
- They provide the best performance and efficiency
- They work well with modern engines that have high-voltage ignition systems
Cons
- They are costly in comparison to other types of spark plugs
- They can be damaged by improper installation or removal
- They may not be compatible with older engines that require a wider gap.
These variations in the material affect your spark plugs’ durability, performance, and cost. They also impact the socket size that fits over them. You should, therefore, know the right spark plug socket size for your vehicle and the appropriate spark plug type for your engine.
Spark Plug Socket Sizes
The sizes of the spark plug sockets act as the shoes for your spark plugs. They have to fit just right over the spark plugs in your engine. These sockets can be anywhere between 8mm and 24mm. Different engines use different kinds and models of spark plugs. The size you need depends on your engine’s type of spark plugs.
The table below shows some of the common spark plug socket sizes and their applications:
| Spark Plug Socket Size (Inches) | Millimetres | Application |
| 5/8 inch | 16 mm | The most common size for modern vehicles, especially those with platinum or iridium spark plugs |
| 13/16 inch | 21 mm | A common size for older vehicles, especially those with copper spark plugs |
| 3/4 inch | 19 mm | A common size for lawnmowers, motorcycles, and small engines |
| 11/16 inch | 18 mm | A typical size for some European and Japanese vehicles |
| 9/16 inch | 14 mm | The common size for some Harley-Davidson motorcycles |
| 7/8 inch | 22 mm | The typical size for some marine engines |
Let’s look closer at each spark plug socket size and how to use it.
● 5/8 inch (16 mm)
The 16 mm spark plug socket is the most common size for modern vehicles, especially those with platinum or iridium spark plugs. These spark plugs have a smaller diameter than copper spark plugs. Thus, they require a smaller socket to fit over them.
● 13/16 inch (21 mm)
The 21 mm spark plug socket size is common in older vehicles, particularly those with copper spark plugs. Copper spark plugs have a wider diameter, requiring a larger socket size to accommodate them.
● 3/4 inch (19 mm)
The 19 mm spark plug socket size is a popular choice for lawnmowers, motorcycles, and small engines. These engines typically have smaller cylinders compared to cars, necessitating a smaller socket size to fit over their spark plugs.
● 11/16 inch (18 mm)
The 18mm spark plug socket size is a common size for some European and Japanese vehicles. These vehicles have different standards than American vehicles and require different sockets to fit over their spark plugs.
● 9/16 inch (14 mm)
Some Harley-Davidson motorcycles use the 14 mm spark plug socket size. These motorcycles have unique engines that necessitate specialized socket sizes to fit over their spark plugs.
● 7/8 inch (22 mm)
Marine engines often require the 22 mm spark plug socket size. These engines have larger cylinders than car engines, requiring a larger socket size to snug over their spark plugs properly.
Also Read : Is it bad to rev your engine in park?
How Do I Know What Size Spark Plug Socket I Need?
Finding the right socket size for your spark plugs doesn’t require you to be a genius. Try these simple methods to get the perfect fit.
● Check your owner’s manual or online
The simplest and most reliable method to determine the right socket size for your spark plug is by referring to your owner’s manual or conducting an online search.
You’ll typically find a dedicated section on spark plug maintenance in your owner’s manual. This section will contain valuable details about the specific type and model of spark plug required for your vehicle, including the corresponding socket size.
You can also search online for your vehicle model and engine type and look for websites or forums that provide this information.
● Measure your spark plug with a caliper or a ruler
You can also use a caliper or a ruler to find the correct socket size. These simple tools can help you measure the width of your spark plug’s hexagon—the part that fits into the socket.
The measurement should match one of the common socket sizes we discussed earlier. For example, if your spark plug measures 16 mm across, you need a 5/8 inch (16 mm) socket.
● Try different sockets until you find the right fit
Another way to find the right socket size for your spark plug is to play a guessing game. Trying this method is risky, as an incorrect guess can harm your spark plug or socket. But if you don’t have any other options, it’s worth a try.
First, gather a set of sockets that cover the common spark plug socket sizes we talked about before. Also, keep a ratchet and an extension bar with you.
Now,
- Connect the ratchet to the extension bar. Then connect one of the sockets to the other end of the extension bar.
- Make sure the socket fits nicely over the spark plug. Then try to twist it a little.
- If it twists easily and smoothly, you have guessed right.
- You have guessed wrong if it does not twist or feels too tight or loose.
- Try another socket until you guess right.
Tools for Removing and Installing Spark Plugs
You’re almost ready to change your spark plugs. But before we jump right in, let’s gather the essential tools you’ll need to make this job a breeze.
- Ratchet
- Extension bar
- Torque wrench
- Gap gauge
- Anti-seize compound
These tools will help you access, loosen, tighten, and secure your spark plugs with confidence and safety in mind.
Step-by-Step Guide to Changing Spark Plugs
Now that you have your tools ready let’s go through the process of changing your spark plugs!
Step 1: Prepare your vehicle and tools
Only change your spark plugs after you have prepared your vehicle and tools.
- Park your vehicle on a level surface and turn off the engine to cool it down completely. The spark plugs can be hot and cause burns.
- Disconnect the negative battery cable from the battery terminal. It’ll prevent any electric shocks or sparks that can impair your vehicle or yourself.
- Locate your spark plugs and wires. Your spark plugs are usually on the top or side of your cylinder head. They are connected to wires that lead to the ignition coil or distributor. You can find out how many spark plugs you have and where they are located in your owner’s manual or online.
Step 2: Remove the old spark plugs
Now you’re ready to take out the old spark plugs.
- Remove one spark plug wire at a time. Do not pull on the wire itself, but on the rubber boot that covers the end of the wire. Twist and pull gently until the wire comes off the spark plug. You can use a spark plug wire puller tool if you have trouble removing the wire by hand.
- Label or mark each wire with its corresponding cylinder number using masking tape or a marker. This will help you reconnect them correctly later.
- Attach the ratchet to the extension bar. Then attach the correct socket size to the other side of the extension bar. Check that the socket fits properly over the spark plug. Then turn the ratchet counterclockwise to loosen and remove the spark plug. Repeat this process for each spark plug you want to replace.
- Examine your old spark plugs carefully. They can tell you a lot about the health of your engine. For example, if your spark plugs look
- Black and greasy, you have too much oil or fuel in your engine.
- White and dry, you have too little fuel or too much heat in your engine.
- Cracked or broken, you have used the wrong socket size or tightened them too much.
Step 3: Install the new spark plugs
Now, it’s time to install the new spark plugs.
- Check and adjust the gap of each new spark plug using the gap gauge. The gap is the space between your spark plug’s center electrode and the ground electrode. The correct gap size depends on your car and engine.
- If the gap is too big or small, it will affect your engine performance. To fix it, bend the ground electrode slightly using the gap gauge until you get the right gap.
- Coat a thin layer of anti-seize compound to the threads of each new spark plug. This will stop them from getting rusty and stuck later. It will also make it easy to take them out when needed.
- Attach the torque wrench to the extension bar. Then attach the correct socket size to the other end. Make sure the socket fits snugly over the new spark plug. Then insert it into the cylinder head.
- Turn the torque wrench clockwise until you feel a click or hear a beep. This means you have reached the correct torque level for your spark plug.
- Repeat this process for each new spark plug you want to install.
Step 4: Reconnect the wires and battery cable
You’re almost done. You just need to reconnect the wires and battery cable.
- Reconnect each wire to its corresponding spark plug using the labels or marks you made earlier. Make sure the wire snaps securely over the spark plug and that there is no loose or exposed wire.
- Reconnect the negative battery cable to the battery terminal. Make sure the cable is tight and not moving.
- Start your engine and check for any unusual sounds or vibrations. If everything sounds normal, you have successfully changed your spark plugs.
FAQs – Finding the Right Spark Plug Socket Size
Q: What size socket for NGK spark plugs?
A: For most NGK spark plugs, you’ll need a 5/8″ (16mm) socket, but always double-check the specific plug model.
Q: Is 5 8 the same as 16mm?
A: Yes, 5/8″ is approximately the same as 16mm.
Q: How many mm should a spark plug be?
A: Spark plug sizes vary. But the most common thread diameters are 10mm, 12mm, 14mm, and 18mm.
Q: Are all spark plugs 14mm?
A: Not all spark plugs are 14mm, but it’s a common size. Check your vehicle’s manual or the plug packaging for the correct size.
Q: Do you need a specific socket for spark plugs?
A: Yes! You need a specific spark plug socket with a rubber insert to protect the plug’s ceramic insulator.
Q: What is the same size as an 8mm socket?
A: A 5/16″ socket is approximately the same size as an 8 mm socket.
Q: What thread is a 14mm spark plug?
A: A 14mm spark plug typically has a 1.25mm thread pitch, but always verify the specifications for your specific plug.
Q: Does M14 mean 14mm?
A: Yes! M14 means 14mm in diameter, referring to the metric thread size.