So oil managed to penetrate your porous surface. You've tried all the methods to pull it out c to no avail and now you fear the entire material needs to be replaced. Fear not... there is a way to still get it out when all else fails.
I installed 170 sq ft of interior tile and cleaned it with mineral spirit oil [as mineral spirit will not allow the grout to stick to the tile making it easier to clean]. For some reason or another, whether manufacturer seal error or bad reaction; the oil penetrated the porcelain. I tried all the methods and nothing worked. Needless to say, the job appeared ruined. Until I researched the evaporation point of oil; which ranges from 576-650 degrees. So I went to ace bought a $40 heat gun and set it to 1100 degrees.
Starting from the center of the effected area, as you want to heat from the center to the edges to prevent cracking, raise the heat gun 1/2 above the stain and move in 2" circles until the oil evaporates. Repeat as needed. Hope this method helps.
