Can I use dielectric grease on the 4-pin connection on the tailgate light bar?

Yes, Dielectric Grease is suggested to provide a barrier to reduce corrosion. Apply a small amount of Dielectric Grease across the female connection points of the 4 Pin Trailer Connector on both the LED Tailgate Bar and the truck. If installing a 2pc Tailgate Light Bar it is also suggested to apply a small amount on the center connection of the bar.