All summer long, according to my gauge. My engine always ran a tad warm at about 200 degrees. I initially thought my cheap gauge could have been off. But, I also felt it could have been accurate being my car took an extremely long time to cool off, but never over heated. I changed a month old 180 thermostat to a 160 in combination to adding water. Previously, I had 100% pure antifreeze. Running a lot cooler now and hovering around 185. I’m sharing this story for anyone that may make the same mistake. Don’t ever use 100 % antifreeze. Lol ! The change should help a ton with my previous vapor lock issue too. Along with a wooden spacer I added.