According to the Vinyl Siding Institute, this is the best way to clean mold and mildew from vinyl siding: Small spots of mold and mildew can be handled with cleaners such as Fantastik® or Windex®. For larger sections, a solution of vinegar (30%) and water (70%) has proven successful. Alternatively, you also could try the following solution: 1/3 cup (2 2/3 ounces) powdered laundry detergent (e.g., Tide®, Fab®, or equivalent), 2/3 cup (5 1/3 ounces) powdered household cleaner (e.g., Spic & Span®, Soilax®, or equivalent), 1 quart (32 fluid ounces) liquid laundry bleach, and 1 gallon (128 fluid ounces) of water.