Guinea pig swallowed syringe stopper/plug!!
Inside the tiny air sacks of the lungs (aveoli) a substance called a surfactant which serves to decrease the surface tension of water in the aveoli and thus increase gas exchange and also prevent aveolar collapse. Surfactants are also commonly included in soaps. Surfactants and oils interact in ways which are functionally fatal to both substances. I assume any oil which is aspirated would cause the same risk of aveolar death and associated lung damage.