Our technicians can evaluate stains and the risk of leaving them in place. We offer soil testing and cleanup services to replace concrete and soil that may have been impacted by the dripping oil filter. Environmentally friendly concrete cleaners are available through Amazon but we have not evaluated the effectiveness of these products. Cleaning a concrete surface does not mean the underlying soil is clean. We try to clean up the stain as best we can. If we feel there is a future contamination risk but the customer prefers to leave the stained concrete/soil in place, we ask these customers to sign a stain sheet acknowledging the potential of contamination under the concrete.