I have this expensive DPDT switch (20A 250V 2hp) which the only problem is dirty encumbered inside. The encumbrance is made of carbonized material and some kind of wax and dirty electrical contacts. The contact poles are in good shape after a good cleanup. I cleaned all part thoroughly. Now it all look clean and neat, ready to reassemble the switch. Since, originally, there was some lubricant inside, that looked like some kind of wax, I am on the search for a similar product.
I recently dipped contacts on a relay (2HP motor) with high temperature silicon grease called Dielectric Grease 67VR. My repair lasted about 3 days (perhaps 20 ON/OFF cycles). The contacts ended up welded together and the grease was carbonated. So, obviously, the dielectric grease is Not a good option.