Diesel Fuel Lubricity: On the Path to Specifications 1999-01-1479

During the last 10 years many researchers and technical groups have studied and performed tests in the area of diesel fuel lubricity [1]¹. Protection of diesel engine fuel delivery system components from excessive wear has been the major mission of these efforts. Understanding of the issue, developing laboratory test methods, specifying appropriate fuel properties, and creating mechanical modifications to the equipment, as well as adding lubricity additives to the fuels, describes the bulk of the work which has been performed in this area.

Technical groups from several organizations such as the Society of Automotive Engineers (SAE), the Coordinating European Council (CEC), and the International Organization for Standardization (ISO) have made substantial progress and some have come up with test methods and fuel specifications [2]. The working group at the American Society for Testing and Materials (ASTM) has been very active in recent years, but has not been able to define a diesel fuel lubricity specification that is acceptable to its members. This group is searching for an appropriate test method and the proper correlation to actual equipment before reaching a consensus on fuel specifications. Other organizations such as the National Conference on Weights and Measures (NCWM) are not involved in the development of test methods. However, they are waiting for the outcome of the work done by ASTM to be able to apply a workable test method in their definition of a premium diesel fuel.

This paper will summarize the efforts of some of these groups and will attempt to spell out the steps necessary to reach consensus on an ASTM fuel lubricity specification. It also presents some encouraging work that has been done with a new Ball on Three Disks (BOTD) test method for measuring lubricity and compares the results to those obtained using the two ASTM methods, SLB-OCLE and HFRR. The results are of interest, specifically, for additized fuels.