If cars run on oil what runs on UFO's?

I just noticed a major question and I had to ask it for the sake of mankind, Oil is usually found on our planet Earth, and spaceships, unidentified flying objects, etc. what in the world are their ships made to run on? Oil is not on any other planet besides Earth, it would kill theirs if they did have oil, so please does anyone know what do UFO's run on? There are certainly no gas stations out there in the universe.