1998 Chevy Cavalier thermostat

You can drive a car without a thermostat as long as you want to but I would recommend replacing it because it controls how hot or cold the air inside your car blows out like without it your heat will not be very warm there not really expensive either at the most $15

Your engine is meant to run at operating temperature. At O/T all the engine internals are at it's proper specification for clearances and what not. When your engine internals are not at these clearances they can produce and create wear within engine which can lead to engine failure. Your thermostat's job is to bring the engine up to operating temp. As quickly as possible to minimize this wear.

Also, without a thermostat the vehicle will run a lot richer (more fuel) which can wreck your catalyst system which can be very costly. And obviously, you'll waste a lot more gas.