This tester comes in two types: (1) the Soda type, which complies with JIS K2519 which tests the extreme-pressure performance and friction performance of lubricants, and (2) the shell-type four-ball friction tester, which complies with ASTM standards. This tester tests and studies the level of boundary friction and the strength of boundary oil films, which give references for comparing the oiliness of lubricants.