Permatex Dielectric Grease #81150. Permatex Dielectric Tune-Up Grease is a silicone dielectric compound used to insulate, lubricate and protect electrical fittings. It protects against salt, dirt, moisture intrusion and stray current in electrical connections. Dielectric grease extends bulb and housing life of navigation lights, masthead electrical connections, trailer lighting and harness or any electric connections exposed to moisture and the elements. Prevents voltage leakage around any electrical connector thereby insuring a strong spark in high energy engine ignition systems.