Not that particular one, but mine also is adj for emissivity. I've found the default is the best all around setting since I'm using it on a variety of surfaces - nitro plugs, batteries, lipos, esc, motors etc. If you are only doing one surface, can maybe adj it to make it more accurate (if its not), but have to have someway to calibrate. Thats the prob. If you've got a friend with a better or diff gun, maybe get an idea on how yours is reading. I used a Raytec for comparison and left emissivity alone after seeing it compared pretty good to the better temp gun.

I have that system too, Sidewinder/5700 and esc has never been over 140F, motor though likes to run around 180F.