A lot of people are misinformed about thermostats and antifreeze. Some people think permanent antifreeze is just that -- it'll last forever. Others think you should remove the antifreeze in the summer and run only water in the cooling system for more cooling.

And there are those who think you should remove the thermostat during the summer months for better cooling. Others think you should leave the thermostat in year-round, but should run a "colder" one in the summer than in the winter.

What should you do about the thermostat and antifreeze? Let's take a look at what the cooling system is and how it works.

Your car's engine produces power by rapidly burning the fuel-air mix that's sent into its cylinders and compressed by the pistons. The spark plug ignites it, and the rapidly burning gases expand, forcing the piston down in its cylinder. The explosion produces tremendous heat, which the cooling system dissipates.

Basically, the cooling system is a series of passages that surround each cylinder. These passages and the radiator are filled with coolant, which the water pump circulates through the radiator. The air being forced through the radiator cools the coolant.

Now, when the engine is cold, you don't want the coolant to circulate through the radiator. So the thermostat is shut when the engine is cold, keeping the coolant inside the engine from circulating.

When the engine and coolant warm up, the thermostat opens, letting the water pump force the coolant to circulate. The thermostat is designed to keep the engine at an operating temperature that provides optimum performance for that engine.

When you remove the thermostat, not only does the engine take longer to warm up, it may never reach its proper operting temperature. Coolant is constantly circulating through the radiator, taking heat away from the engine when it shouldn't be.

For best engine performance, the thermostat should be left in the engine, and it should be the one that the maker put in the car. If it must be replaced, it should be replaced with one that has an identical operating range (some thermostats open at a lower temperature than others).

What about antifreeze? So-called "permanent" antifreeze is not permanent. The coolant gets dirty, and the antifreeze "wears out." Coolant should be drained and replaced every two years; hoses and belts should be replaced at this time also.

Nor should you run straight water -- a mixture of water and antifreeze offers more cooling than water alone.