I can share a funny story about this stuff. In my younger days, I had blown a head gasket in a little 4 banger. Water was being burned in the combustion chamber, not going into the pan. A buddy of mine at the auto parts store "gave" me 4 bottle of the stuff for an experiment. We drained the oil and replaced it with slick 50. I drove that car to and from work with a blown head gasket, 25 miles round trip on the interstate for a month.(speeds up to 80 mph) The temperature gauge never went above 2/3 of the way up, never into the red zone and the car drove great. It lasted me that way until I could get it fixed. Turns out the head even had a crack in it. The bottom line though was it did do something to limit friction which had an affect on limiting heat. Whether or not it would do anything for a good running car or something larger than a little 4 banger is still a topic for debate. I can still laugh about that because damn if it didn't get me by for awhile.
I wouldnt use it BUT most of the info you find is a little outdated. I dont see the potential gains overcoming the cost - especially since I dont think WE would gain anything measureable.