Thermostat Question

[Mopar1]

I ll see if I can explain this rite. When running the car in the daytime the temp( stock ) gauge stays on the second bar up from the 130 mark. At night it stays between the second bar and the half way mark on the gauge. The car seems to run better at nite time with this warmer reading. I also looked at a guys GT the other day and he had a much smaller radiator then mine. He said his was stock. I enclosed a pic of my radiator, that I assumed was stock until I seen his.

I am thinking about going back to a 190-192 deg thermostat when my intake comes in next week. The car seems to run better on the warmer side at night.. Theres a 180 deg thermo in it now. I was guessing that maybe it wasnt running in a closed loop during the daytime due to the larger radiator and 180 thermo in it now.

Is this the wrong way of thinking.