What kind of socket do I need to change spark plugs?
The short answer: you need a spark plug socket that fits the plug’s hex size (most modern cars use 5/8-inch or 13/16-inch), and it should be a deep-well socket with a retaining feature, paired with a 3/8-inch or 1/2-inch drive.
In practice, spark plug sockets are designed to reach recessed plugs and grip them securely without dropping the plug into the engine bay. Hex sizes vary by engine and plug type, so confirming the exact size before you start is essential. If you’re unsure, check the vehicle’s manual or measure the plug across its flats with a caliper or ruler. Note that this guidance focuses on gasoline engines; diesel engines use glow plugs, which may require different tools and approaches. Always verify with the manual or a professional when in doubt.
Common spark plug hex sizes
Most engines use one of a few standard hex sizes. The following sizes are the ones you’re most likely to encounter. Always verify the plug you’re removing.
- 5/8 inch (16 mm) hex — the most common size for modern gasoline engines. Use a deep-well spark plug socket that matches this hex.
- 13/16 inch (21 mm) hex — used on some older or specialty engines; may require a larger deep-well socket or a 21 mm spark plug socket.
- 14 mm hex — a metric alternative found on certain engines; check your plug or vehicle manual.
- 3/4 inch (19 mm) hex — rare, typically seen on some heavy-duty or high-performance engines.
In short: the hex size is the key factor. If you’re unsure, measure the plug or consult the manual to pick the correct socket size.
Key features to look for in a spark plug socket
Beyond the hex size, the socket’s design matters for reach, retention, and ease of use. The following features will help you work cleanly and safely.
- Deep-well design to reach recessed plugs without hitting the sides of the spark plug well.
- Rubber insert or magnetized core to hold the plug securely while you loosen and remove it.
- Appropriate drive size: 3/8-inch drive is standard for most cars; 1/2-inch drive is common for larger trucks or higher-torque tasks.
- Quality material and corrosion resistance; a non-slip coating can extend life in damp environments.
Choosing a deep-well, retention-equipped socket in the correct hex size and drive size will reduce the risk of damaging the plug or dropping it into the engine bay.
Tips for using the socket safely
Before you begin, ensure the engine is cool, the battery is disconnected if needed, and you have the right replacement plugs. Work calmly to avoid dropping tools into the engine compartment, and use a torque wrench to reach the manufacturer’s specified torque. If your vehicle uses anti-seize or specific gap settings, follow the OEM guidance rather than applying generic practices.
Summary
To change spark plugs successfully, start with the socket that matches the plug’s hex size—most commonly 5/8" or 13/16"—and choose a deep-well design with a secure retention method. Pair this with the proper drive size (3/8" or 1/2") and quality construction. Always verify the exact size for your engine in the manual or by measuring, and follow torque specifications and safety steps for a clean, trouble-free replacement. If in doubt, consult a professional to confirm the correct socket for your specific model.
What socket do I need to change spark plugs?
For the majority of plugs, you need a 5/8” or 16mm socket. Some Fords use 9/16″ plugs, some newer European and Asian vehicles use 14mm plugs, and there are a few applications that use 7/8″, 13/16″, ¾” or 18mm plugs. All spark plugs are 6 sided, except some BMW engines.
What size ratchet do you need for a spark plug?
Most spark plugs require a 5/8" (16mm) size spark plug socket. This refers to the size of the flats on the spark plug that are in contact with the socket. This spark plug requires the 5/8" spark plug socket, which will probably fit a 3/8 ratchet extension.
Can I remove a spark plug with a regular socket?
You can reach down. Inside. Put it on the put the rubber hose on the spark plug insulator. And you can now pull the spark plug. Out same thing when you go to put a new spark plug.
What tools do I need to change my spark plugs?
Gather needed tools and parts - a set of spark plugs, a ratchet, a spark plug socket (make sure you have the right size), extensions, a gapping tool, and dielectric grease. Other hand tools may be needed on some vehicles.
