&rdquo Clean products&rdquo refer to light, refined oil products such as jet fuel, gasoline and naphtha. These products are usually carried in clean, coated tanks. &rdquo Dirty products&rdquo include heavy oils such as crude oil or refined oil products such as fuel oil, diesel oil or bunker oil. If a product tanker carries &ldquo dirty products&rdquo , it will require particularly thorough cleaning if the vessel is subsequently to transport &ldquo clean products&rdquo .

  Product tankers are characterised by having coated tanks to prevent corrosion from the refined products and to facilitate cleaning of the tanks. Especially for the transportation of &rdquo clean products&rdquo , there are strict requirements that the tanks must be completely clean before a new product is loaded, because the products must have as high a degree of distillation as possible. Furthermore, to ensure as clean a product as possible, the oil companies often stipulate which type of products the tanker must recently have transported.