Spark Plug Sizes Socket Guide

Spark plugs are a vital combustion engine component that will ultimately wear out. On older vehicles, the task was straightforward as nearly every spark plug was the same size, or there were two at most. However, things change, and you can find numerous HEX sizes for nearly all spark plugs for many engines.

Car imports are one area that differs, and many gardening tools that have engines running on gas, such as lawnmowers. All have different sizes, and thus replacing spark plugs can require a spark plug socket rather than a dedicated spark plug wrench.

Besides this, manufacturers design engines where you can’t easily access the plugs. This requires a deep spark plug socket where a rubber grommet holds the plugs in place. Size is the most crucial issue, so that you can use our spark plug size chart; you’ll be able to figure out the various spark plug size socket that goes in which engine.

Spark Plug Sizes and Sockets

By the end, you can easily see the right spark plug socket size for the engine and the HEX size you have. (Learn How To Unscrew Triangle Screws Without Screwdriver)

Are There Different Size Spark Plug Sockets?

You can see additional sizes of spark plug wrench size offerings in your socket set. Yet these cover the most common size rather than all variations you can find.

You may ask the most common sizes of spark plug sockets, and by checking your plug socket set, you’ll see there’s no standard size for spark plug sockets.

Standard plug socket sizes are commonly mistaken, with the most popular sizes of the socket being 13/16′′ and 5/8′′.

Although 3/4″ plug sockets are widespread in lawnmowers, these sizes are primarily seen in automobiles. As a result, standard formats are available; however, they differ based on the vehicle.

It’s not too tough to determine the correct spark plug socket size, but some individuals get this wrong.

Follow a couple of steps below to determine the size of the spark plug socket.

First, look in your manual for the kind and model of the pre-gapped plug. This simplifies determining the socket size. It is handy to have a gapping tool to adjust your plugs rather than buy new ones.

Look at the spark plug itself to see what size socket it has. Vernier calipers can be used to measure the HEX size or diameter if you have them.

Hex refers to the socket or diameter of a spark plug and the faces used to loosen or tighten using your spark plug socket.

You can find the spark plug socket size chart here, and it shows the most common plug sizes and the vehicles on which they are used.

Because of how the engine world works, there are no direct conversions of spark plug sizes to mm or metric. Instead, all sizes are listed in imperial, which is the global standard.

Spark Plug SizeApplication
14mmAsian or Newer European vehicles and some motorcycles
5/8"Newer vehicles: GMC, Chevy, Nissan,Subaru. Small engines: Briggs & Stratton, Koehler etc.
11/16"Older BMW vehicles
18mmMany motorcycles, and small engines
3/4"Lawnmowers, small engines, and older GM vehicles
13/16"Older large engine vehicles
7/8"Aviation, tractors, and older vehicles

It is important to note that you should utilize a torque wrench when inserting your spark plug. This is because overtightening the plug and stripping the cylinder head thread can be avoided using a torque wrench tool.

A socket wrench of this type should accommodate a variety of sockets, or an adapter will be included to allow the tool to suit a variety of sizes.

Different Spark Plug Socket Sizes

Spark Plug Socket Sizes

A few deep spark plug sockets and ordinary spark plug sockets are available.

When dealing with a recessed plug, deep sockets are significantly superior.

In confined spaces, universal joints might make using the correct spark plug socket easier. You may move the wrench across one axis while rotating the sockets along another axis, thanks to the articulated joints. (Learn How To Remove A Stripped Hex Screw)

Spark plug sockets for the right spark plug socket and fitting specific engines are sold separately.

However, you can find kits comprising various socket sizes that include regular spark plug sockets and deep spark plug socket. With these, you’ll also get sockets with a rubber boot and extensions and possibly a universal joint for certain engines.

Because of their unique purpose and length, 7/8″ sockets are rarely included in socket sets and require a 1/2″ drive.

Several sockets are available in 12-point forms, but the 6-point version is more popular. Only a few autos employ 12-point plugs, such as certain newer BMW engines, which also use deep socket.

Removing these may need a universal joint and deep socket as many sockets and a regular socket wrench can’t fit in the confined spaces inside the engine bay. Most other cars have more room to fit your plug socket and socket wrench.

Are spark plugs the same size?

Spark plug sockets are explicitly made for spark plugs. They have two interiors, each securely holding the plug without destroying it.

For example, magnetic sockets employ magnets to keep the plug insulator in place, whereas rubber inset sockets create a soft rubber cradle for the plug to rest in.

While this may not seem like much compared to the various deep socket sizes, it can make a big difference. The unique bed prevents sliding during installation and removal, allowing faster installation and removal.

When spark plugs are located deep within the engine block, you may also need an extension on some autos; this can save a lot of time and a few bruised knuckles. In addition, using a spark plug socket eliminates the risk of harming the insulation.

Spark Plug Socket Sizes

There are only a few deep and standard spark plug socket set options. Deep sockets work better in a sophisticated automotive engine like a BMW when dealing with recessed plugs.

Most sockets are 3/8″ drive compatible (square lug size on socket wrench), although some kits may include one or more extensions or swivels. Thin walls are preferred because they make access to deeper depths easier.

Special Spark Plug Socket

Spark plugs come in two sizes: 5/8 inch and 13/16 inch. In addition, most spark plug sockets have a rubber insert that secures the plug firmly in place.

When you turn torque wrenches, a gauge shows how much torque is exerted.

Some wrench models let you set the level of torque, and thus it is impossible to over-tighten a socket, be it a regular-sized or up to a 16 inch bolt.

Universal joints may be useful if you can’t fit a wrench and extension into the space surrounding your spark plugs.

With these tools and supplies, you’ll be ready to tackle any problem that may arise, from little repairs to major repairs.

Unlike regular socket wrenches, spark plug sockets are specifically engineered to attach to spark plugs without destroying them. You can find two main connection methods with magnetic sockets that use magnets and rubber inset sockets that use gentle force to keep the car’s plug-in the socket.

This means the spark plug insulation or even the car’s engine block is less likely to be damaged. In addition, a special bed on spark plugs prevents them from falling out of the socket. As a result, engine components installation and maintenance can be accomplished quickly.

A plug falling out of your spark plug socket means the gap can close, and you’d need to use your gapping tool again or change the plug for a new one. In the same way, when fitting hex bolts in confined areas on a car, you need them to be secure.

Many cars’ spark plugs are hidden deep within the engine block; thus, this will make a massive difference to owners.

Because of the spark plug size, they are less concerned about damaging any part of the car, such as stripping threads or dropping the plug.

Guide in Installing Spark Plugs

Spark Plug Installation

Here you can find some quick guides on installing spark plugs using your spark plug socket.

You will need to do this if your engine isn’t running right. Here’s how you can tell you need to clean your plugs or replace them. (Read What Can I Use Instead Of A Screwdriver)

What a Spark Plug Misfire Feels Like

The following are some examples of how a spark plug misfire could feel.

Loss of Power

When an automobile struggles to deliver power, it’s a sign that the spark plug has blown. It feels like the vehicle is shaking and not accelerating correctly. Finally, it comes to a halt on all cylinders.


The engine’s sound varies because all the cylinders are not working efficiently.


Because the cylinder walls were leaking, the automobile’s inside smelled like oil as fuel wasn’t being burned.

Smoking Emissions

You may see smoke pouring from the engine exhaust as the plugs are not igniting fuel as they should do.

Installing Spark Plugs

1. Set The Gap

Previously, you had to establish the gap on a new spark plug before it could be installed.

To ensure that you have the correct sized spark plug, you can use a gapping tool. However, even if today’s spark plugs are pre-gapped, it’s a good idea to double-check the owner’s manual for such instructions.

If you can’t get a tool to check the gap, one pro tip is using a matchbox to measure the gap. It may not be exact, yet it is close enough for most engines.

2. Seat Your Plug

After you’ve placed the plug by hand, tighten it with a torque wrench. Make certain not to overtighten it. Continue spinning until the washer on the plug touches the mounting surface.

3. Insert the Plug Into The Spark Plug Socket Boot.

The ignition coil and the wire connector should be replaced. When installing the wire plug, make sure you hear a click.

That would indicate that it has been installed. If you’re going to use a rubber boot, a coat of dielectric grease inside it is a smart idea. That way, you may easily remove the plug.

You’ll need to do this for how many plugs your engine has. For example, a lawnmower would be one, and your car can average around four depending on the model.

Spark Plug Sizes Socket Guide