This paper assesses the impact of esters of monocarboxylic fatty acids, on the lubrication properties of ultra-low-sulfur diesel fuels. Seven esters were used as lubricating additives on a matrix of eight fuels, at five different concentrations of 50, 100, 500, 750, and 1000 ppm. Tribological experiments carried out on the high-frequency reciprocating test rig (HFRR) showed that the effective concentration of the additives was 500 ppm or higher.