Q: Safe to drive if thermostat needle fluctuates but car doesn't run hot

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Car ran out and found that coolant was low. After adding coolant and started driving on street, thermostat needle fluctuated towards hot. When I slowed, it leveled to middle. Is thermostat broke and is it safe to drive to mechanic? I am not seeing any leaking.

My car has 211000 miles.
My car has an automatic transmission.

Hi There, It sounds like your thermostat in your cooling system is sticking causing the temperature gauge to fluctuate as you have indicated. The thermostat regulates the flow of the coolant in your car’s engine and controls when the coolant flows in and out of the motor from the radiator by opening and closing at specific temperatures. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. When the thermostat is stuck open it can cause the coolant to circulate constantly resulting in the motor never reaching the correct operating temperature. In order to avoid any potential damage to your engine, would suggest scheduling an appointment to have one of our experts come to your location to inspect and repair your vehicle.

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