Fuel Lubricity Reviewed

Many components on both aircraft and ground vehicles rely on fuel for lubrication and cooling of sliding contacts. Reliable performance of these power sources depends on the fuel providing sufficient lubrication to protect each of the many contact types within the pump and injection system. This characteristic of fuel has come to be known as lubricity. The subject of fuel lubricity has gone through a number of phases, most of which resulted from changing the composition of the fuel, which historically has been driven by fuel stability and by environmental regulations. This paper reviews these phases in chronological order. Beginning with the fuel system failures reported in aviation equipment in the 1960s and 70s, through the Military experience with low lubricity kerosene fuels in compression ignition engines in the 80s and 90s, to the ongoing introduction of more severely refined diesel fuel in progress in many developed countries around the world. The paper tracks the principal wear mechanisms observed in each instance, along with the laboratory-scale wear test procedures that were developed to simulate the condition. A complete description of this rapidly developing subject is beyond the scope of the present publication. However, it is hoped that the more salient issues are addressed, with numerous references also given to allow the reader to easily obtain additional information if needed.