Dielectric grease. It was commonly used in old TV sets for high and low amp switches. Dielectric grease is neither a conductor nor an insulator of electricity. It lubricates, protects against corrosion, and apparently gets out of the way to allow full current to pass between switch contact areas.
Use of a conducting type grease for a switch may cause a current bleed, as it contains electrical conducting compounds.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission