The component in a car that informs the driver about the amount of fuel left in the tank is called a "fuel gauge." The fuel gauge is typically located on the dashboard of the vehicle and provides a visual indication of the fuel level, allowing the driver to monitor when a refill is required. The fuel gauge works in conjunction with a sending unit in the fuel tank, which measures the actual amount of fuel present and sends this information to the gauge for display. If the fuel gauge is not functioning correctly, it may require servicing or replacement to ensure accurate fuel level readings.