No. In the diagram that dave-in-nj posted, Vin is the car battery + terminal. Vout = Arduino analog pin. R1 is for example 3.3k or 3.9k resistor, R2 is 1k resistor. You will also need to connect an Arduino GND to the car battery - terminal.
But please take note of the advice to use a zener diode to protect the input from an unusually high voltage from the car battery charging circuit.