In Indiana since there is no law mandating the emplyer to reimburse the emplyee for milage or gas when the emplyee is required to drive their own personal vehicle for work related thing can an emplyee be fired for refusing to use their own vehivle? (employer use to pay for milage and then just one day deciced to stop)

Since there is no law prohibiting an employer from requiring an employee to use their own vehicle, yes, they can.