Di-electric grease

[Brewsterbuff]

Is Di-electric grease a conductor or an insulator? I was always under the impression it was a conductor, put it on my battery clamps and a thin coating on the light bulbs to reduce corrosion and make a better connection. I used it on all the old cars and on several trailers. It never gave me a problem? Recently a battery guy laughed, said I was wrong, it was an insulator and would weaken my connections. Cold here today. ??? tomorrow.