They are mounted on the cylinder head(s) and the equipment required to change them are a spark plug socket compatible with a ratchet, various extensions, a gap wire used to check the gap of the new spark plugs and a torque meter used in tightening. It is also good to have new plugs and adjust their gap before fitting them; it is also recommended that they need to be changed one at a time so as to ensure that the correct type is provided for the specific engine. It is advisable not to pull out the removed plugs until the engines have cooled when already on the garage floor make sure that the new plugs do not have any defects and that the gap is right. Using the proper thickness-gauge one checks the gap and if the gap is to be adjusted, then one should bend the side electrode properly because bending it roughly may cause some harm to the porcelain insulator. For V6 models, air intake duct could be detached and on V8 models, rear bank ignition coil mounting bracket could be unbolted to provide good access to the rear spark plugs. When disconnected the spark plug wire, pull only the boot, if necessary twirl compressed air to blow into the spark plug hole. To take off the spark plug, use the socket and turn it anti-clockwise, then examine the old plug relative to the new spark plugs for the condition of the engine when running. If one is changed with bare hands, screw in a new plug until the last turns are very tight, then tighten it to preset standards with the help of a torque wrench or a ratchet; a short rubber hose is useful to thread it home without risk of cross-threading. Before fitting the spark plug wire to the new plug turn it round and round in order to have a tight connection for all the spark plugs in place so as not to confuse the wires while replacing each of the plugs separately.