I believe stock t-stat is 180F. The best you can keep the engine in that neighborhood the better. Where you live, aluminum would probably be best. My CSF does fine where I am at and in the winter I am at 174F most of the time to 184F on load. In the summer I can get warmer and traffic doesn't help. I watch out for anything over 204F and will pull off and let things cool off if i get much over that.
