SMOKE WAS NOTICED INSIDE THE CAR WHILE I WAS DRIVING ON A RURAL FREEWAY IN THE BLUE MOUNTAINS OF OREGON. THE SOURCE OF THE SMOKE APPEARED TO BE THE REAR PASSENGER SET, RIGHT SIDE. I PULLED OVER. WHEN I OPENED THE DOOR ON THE RIGHT SIDE OF THE CAR, A LARGE PLUM OF SMOKE ERUPTED FROM THE REAR SEAT. I THEN NOTICED A BLACK, BURNED HOLE IN THE SEAT MEASURING ABOUT 10IN X 10IN. AS QUICKLY AS IT BEGAN, THE COMBUSTION STOPPED. AFTER A 20-MINUTE WAIT THE SEAT COOLED OFF AND I WAS ABLE TO PROCEED. NOTE THAT THE REAR SEATS WERE IN THE DOWN POSITION, AND PILLOWS WERE PLACED ON THE FLOOR BOARDS WHERE PASSENGER FEET WOULD NORMALLY BE.PHOTO SHOWS DAMAGE TO THE PILLOWS. I SUSPECT THE ORIGIN OF THE FIRE WAS AN ELECTRICAL FAILURE RELATED TO HEATED SEATS.