Challenger PC-737 is a strong concentrate that can be diluted with water. When diluting, your best guideline is “the greasier the surface, the more Challenger you’ll need in the mix.” To apply Challenger: First, spray the surface to be cleaned with Challenger. Give the Challenger a little time to penetrate the grease and grime. Then rinse well with water (preferably hot or warm, but cold water also works well).