When I moved to the Tucson area my car had a 160 deg thermostat which in traffic allowed heat to build to point of spitting out my overflow. I also had an aluminum radiator. I switched to 190 deg thermostat to increase dwell time in radiator. Worked well to solve my problem. For me it seemed counterintuitive to solve the problem, but it did work in my case. Glad I listened to radiator guy.