A study on the possibility of the Brugger test application for differentiation between the API GL performance levels of gear oils

The paper presents the results of research aimed at differentiation between the API GL performance levels of automotive gear oils. Tribological tests were conducted with the use of two different tribotesters. A four-ball apparatus and a crossed-cylinder wear tester were employed. Several dozen oils were tested, and various standardised measurements of their lubricating properties have been determined. Then, the measurements of the tribological properties were related to the particular API GL performance levels and the results obtained in the two tribotesters were compared. The most known measurements, which characterise the antiwear and extreme-pressure properties of lubricants, were determined with the use of the four-ball apparatus. Using the crossed-cylinder wear tester, the load-carrying capacity of the oil has been assessed through the Brugger test. The statistical analysis of the research results has shown the possibility of the differentiation between the API GL performance levels of automotive gear oils on the basis of the Brugger test. The Brugger test is characterised by relatively low time-consumption, and the crossed-cylinder wear tester is relatively inexpensive, thus this approach may give significant benefits to the laboratory testing automotive gear oils.