Just wondered. I set the idle on my 1978 450SEL and travel up North to a much Higher Elevation. The idle change about 300 RPM and the the automatic transmission stated to shift harder. When we returned, the idle went back to were I had set it and the transmission started to shift smoother. In the valley of the sun the temperature is about 106F right now. It was about 93F were we were staying. I would not think the temperature would of affected it. Not sure what to look for or why. Any suggestions would be truly appreciated.