PLUG STUDIO / NGK

Is there a specified tightening torque for the spark plug?

The tightening torque for a spark plug changes with the diameter of the spark plug.
The following are the recommended torque values.

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When installing the spark plug, first screw it in by hand. Once the gasket has made contact with the cylinder head, use the torque wrench to tighten it to the tightening torque shown below.

A rubber pipe as shown in the figure to the right is a good substitute for hand tightening/removing spark plugs.

Tightening torque

Plug thread diameter	Tightening torque
18 mm	35 to 40N·m (3.5 to 4.0 kgm)
14 mm	25 to 30N·m (2.5 to 3.0 kgm)
12 mm	15 to 20N·m (1.5 to 2.0 kgm)
10 mm	10 to 12N·m (1.0 to 1.2 kgm)
8 mm	8 to 10N·m (0.8 to 1.0 kgm)

Tapered seat type For (spark plugs without gaskets)

Tightening torque
10 to 20 N·m (1.0 to 2.0 kg-m)

The tightening angle for both new and reused spark plugs is 1/16th of a turn.

For reference

When it is difficult to use a torque wrench, or when you don't have a torque wrench, tighten the spark plug to the tightening angle shown in the illustration in accordance with the thread diameter of the spark plug.

Spark plugs with thread diameter of 18 and 14 mm

Spark plugs with thread diameter of 12 and 10 mm

Spark plugs with thread diameter of 8 mm

* There are some exceptions. Look at the adaptation for more information.

Examples of common installation problems and advise to avoid them.

Thread damage from installation	Metal shell damage	Cracked insulator	Examples of bad spark plug wrench usage

Spark plug is inserted at an angle during installation	Excessive tightening torque	Spark plug wrench slipped or used at an angle
Do not use the wrench at first. Start by installing the spark plug by hand.	Tighten to recommended torque.	Use a hex-type wrench that is less likely to slip.

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