Spark plug wires
Spark plug wires (also called high tension leads) are electrical cables used by older internal combustion engines to transmit high-voltage electricity from the distributor to the spark plugs . Tension in this instance is a synonym for voltage. High tension may also be referred to as HT. Many modern engines use coil-on-plug ignition, a design that does not use spark plug wires. Design Spark plug wires have an outer insulation several times thicker than the conductor, made of a very flexible and heat-resistant material such as silicone or EPDM rubber. The thick insulation prevents arcing from the cable to an earthed engine component. A rubber "boot" covers each terminal. Dielectric grease can be used to improve insulation; a small amount can be applied in the inside of the rubber boot at each end of each wire to help seal out moisture. Printing on spark plug wires may include a brand name, insulation thickness (in millimeters), insulation material type, cylinder number, and conductor type (suppressor or solid wire). The wire from each spark plug is just long enough to reach the distributor, without excess. Each lead contains only one wire, as the current does not return through the same lead, but