This part specifies the classification principle of lubricants, industrial oils and related products (L category), which belongs to the first part of the GB 7631 series of standards. In this classification, products are divided into 18 groups according to the principle of including as far as possible all applications of lubricants, industrial oils and related products. The detailed classification of each group is given by other parts of GB/T 7631. This category applies to new products only.