Others may be right about 180 degree thermostats being better for the fuel mix or engine wear, I don't know. But the Roadrunner always liked running as cool as possible and seemed to run better on a 160 degree so that's what I always ran. Maybe it had something to do with the meager 22" radiator it came with so I may revisit this since I'm upgrading to a max cool 26" aluminum radiator.