Is it a good idea to move from Synthetic oil to normal oil ?

[dogsridewith]

Yes. Higher ambient gives higher coolant and oil temperature. Thermostats, or most thermostats, don't flip from full closed to full open at one temperature. In cold winter, a temperature gets maintained with little coolant flow. So the thermostat isn't very far open. In sweltering heat, the temp may not stabilize until the thermostat is nearly open. And more open takes a higher temperature. The thermostat has an opening versus temperature curve.

And coolant doesn't cool some places so well. The oil pan can be getting radiation and conduction from sub freezing pavement/air or very hot asphalt and the air it heats.