Whist I understand the improvement at idle or low speed, it doesn’t really make sense why temps dropped at highway speeds. The fan is pretty redundant at high speeds unless you’re crawling very slowly laboring up a mountain pass.
After about 1 year after initially installing new plugs, I decided for my pre road trip check list, to check the torque. 2 were kinda hand tight, 4 were tight but got more from them, and 2 were snug even though I gave them a tiny bit more.