The fuel gauge in the car starts to light up: How many kilometers can I still manage “in reserve”?. As a rule of thumb, there is usually around 50 kilometers left when the display lights up.
ADAC tests show that as a rule, you get further than the on-board computer predicts. Anyone left with an empty tank will face a fine. While there is no risk of trouble in the event of a breakdown, the situation is different if the vehicle breaks down due to a lack of fuel.