Is it true that the thermostat remains open whenever the car reaches its normal operating temperature? So, consequently, it doesn't matter if I have one or not as I live in a tropical region.
Yes, for most intents and purposes, if you live in a tropical region a lot of people take their thermostats out and don’t need them.
Now, there are certain cars (some high-tech cars) that are made to run with a thermostat. It’s just the way their cooling systems are designed and if you take the thermostat out, the water wouldn’t stay in the radiator long enough to dissipate heat and it might start to run hot.
In that case, you’d need to put the thermostat back in. But on most normal cars, such as Ford, Chevy, and Toyota, if you live in a tropical area and you take the thermostat out, you really aren’t going to have any problems. It would run okay. But you still need to use coolant and not just water. If you use water, I know it’s not going to freeze like it would up North and break everything because ice expands when it freezes. However, you still need the anti-corrosion additives of antifreeze. So make sure to use 50 % antifreeze with 50 % water whether you are running a thermostat or not.