Which was does a thermostat go in car?

A car thermostat is installed in the engine's cooling system, usually in the lower radiator hose or in the engine block itself, depending on the vehicle's design. There's no single "which way" as the orientation depends on the specific thermostat and its housing. The thermostat itself usually has a small arrow or marking indicating the direction of coolant flow. Always consult your vehicle's repair manual for the correct installation procedure and orientation. Incorrect installation can lead to overheating.