The problem with temp guns is that they don't actually measure temp, they instead measure the infrared light then they compute what a 50% grey body's temp would be if it radiating the same infrared light. A shiny polished aluminum Fox engine would be running hotter than a black Saito BK if the temp gun said it was running at the same heat. Or in other words if a shiny polished metal and a black metal were at the same temp the temp gun would say the black metal was at a higher temperature. Good for comparison for the same engine with the same equipment and fuel only.