I've only had one engine that ran better cool - my '86 Ford bus with the 370. Every fall I changed it to 192 thermostats to keep passengers warm. Every spring I change it to 160's. It had more torque cooler. With a 370 and 71 passenger I needed all the help I could get.
My usual plan is get them to run as warm as I can as long as they are consistent. Idle them a few at shutdown and walk away.