A method of final washing of biodiesel through air agitation. Biodiesel floats above a quantity of water. Bubbles from an aquarium pump and air stone are injected into the water causing the bubbles to rise. At the water/biodiesel interface, the air bubbles carry water up through the biodiesel by surface tension. Simple diffusion causes water soluble impurities in the biodiesel to be extracted into the water. As the bubble reaches the surface and breaks, the water is freed and percolates back down through the biodiesel again.