Would like to know if someone could tell me the difference between a 160 degree and a 195 degree thermostat.

We are having a discussion on a car forum I belong to and some of the guys maintain that the higher temp thermostat will make the car run hotter. I always thought that the thermostat wouldn’t change the maximum temp, but would only delay reaching the maximum due to the fact that it opens sooner and allows circulation, thus slowing down the heating up process.

What’s the real answer. Thanks.


Well, it depends - certainly, once it’s open, if the car’s stable temp is, say, 210, it’ll be 210 with either thermostat. This ignores the time it takes to get to 210, though, so a ‘hotter’ thermostat will result in the engine being at a higher average temp for the time before it stabilizes.

The temperature rating of a thermostat is the temperature at which it opens, so a 160 degree thermostat opens at 160 and a 195 degree thermostat opens at 195, etc.

Modern engines are designed to run at higher temperatures than older engines, hence the use of 195 degree thermostats or even higher. The higher temperatures support more complete combustion, and the higher rated thermostats help the engine warm up more quickly, which reduces pollution.

A higher temperature thermostat will NOT make an engine overheat, assuming it is designed to run at this temperature and has the proper radiator cap in place.

A lower temperature thermostat is not “better,” nor will it solve an overheating problem.

It really does depend on the type of car, ambient temperature and how hard the engine is working.

On some cars in more extreme conditions, the thermostat will work like you imagine with the thermostat opening up and staying open, therefore same temperature no matter what. But most cars these days have over-built cooling systems that are designed to keep the engine cool driving 100 MPH up a hill in the desert in the middle of July with the A/C on. On these, if engine load and/or ambient temperature are less extreme, when the thermostat opens the cooling system will eventually make the coolant temperature drop back below the open point for the thermostat and it’ll have to close up again to maintain it. So therefore, a hotter thermostat will on average make it run hotter.