Untreated concrete is not water- or oil-resistant. If water spills on the floor, it gets absorbed, then gradually resurfaces and evaporates, creating a slippery surface. However, oil is assimilated into the concrete and changes the chemical structure of the floor. If the floor is coated, the concrete will sweat out the oil, cause bulges, and degrade the paint faster. This means the floor will need to be removed and repoured, then coated to remove the contaminated areas.