In diesel engines, fuel pumps and injectors are subjected to tremendous pressures that can reach upward of 200 MPa in modern systems. In order to generate and maintain this level of pressure, the internal pump and injector components are made to an exacting standard. The drawback is that the moving components are largely lubricated with just the diesel fuel. If the diesel fuel has insufficient lubricating quality, catastrophic wear and subsequent failures can occur.
The US Army currently utilizes aviation turbine fuel in all of its diesel-powered ground vehicles. The current specifications outlined in MIL-DTL-83133, Turbine Fuel, Aviation, Kerosene Type, JP-8 (NATO F-34), NATO F-35, and JP-8 + 100 (NATO F-37), and ASTM D1655, Standard Specification for Aviation Turbine Fuels, allow specific synthetic fuel components that can exacerbate the lubricity issue (having both low viscosity and no aromatic content). With these synthetics, the High-Frequency Reciprocating Rig (HFRR) can have a wear scar diameter as high as 900 μm, which, if run unadditized in an engine, will cause immediate hardware failure. The military requires the use of an approved lubricity additive in the fuel it acquires. If treated with an approved additive at a rate between 20 and 30 mg/kg, even these poor lubricity fuels will be able to operate in Army equipment for the life of the engine. Unfortunately, the HFRR wear result does not discriminate between these neat and additized fuels. This work was undertaken in an attempt to improve the correlation of HFRR-type wear scar results with pump test results for a series of fuels with varying levels of lubricity additive. The effects of varying test conditions are reported and conclusions drawn on how improvements could be made to the current lubricity testing standards.