WE HAVE A KIA SORENTO 2012. PASSENGERS SMELLED GAS 4.5 HOURS INTO A 5 HOUR TRIP TO PHILADELPHIA. STOPPED AT REST STOP AND DID NOT THINK IT WAS COMING FROM CAR. WE DROVE APPROXIMATELY ANOTHER 30 MINS INTO PHILADELPHIA AND GOT OFF THE HIGHWAYS ONTO LOCAL STREETS. JOGGER ON SIDE OF ROAD FLAGGED US DOWN WITH "YOUR CAR IS ON FIRE!" WE PULLED TO SIDE OF ROAD AND GOT OUT OF THE CAR. THE KIA SORENTO'S ENGINE WAS ON FIRE. A LOCAL FIRE DEPARTMENT ARRIVED AND PUT OUT THE ENGINE FIRE WITH WATER. NO INJURIES.