When use this product to clean the engine surface.it can rapidly penetrate into the inside and out of the stain and slowly emulsify the stain.it just need only 2-5minutes.the stain can be peel off from the engine.This product is not flammable.It did not need any protection while cleaning.This product can emulsify the oil stain into water.and the water can be degradation in nature.no pollution to the nature.