This standard specifies methods for the determination of alkaline components in petroleum products and lubricants. Based on the ratio of ionization constants of strong and weak alkaline substances, alkaline components are classified into two groups: strong alkaline and weak alkaline. It is suitable for samples with a base number of less than 70 mgKOH/g. The measured base number is usually used to describe the change of oil under conditions such as oxidation, but it cannot directly predict all alkaline changes in oil products, such as those related to internal corrosion and abrasion of machines. This standard replaces the method for the determination of base number in the 1987 GB/T 7304 standard.