The Influence of Fatty Acids and Fatty Acids Mixtures on the Lubricity of Low-Sulfur Diesel Fuels

Research described in this work relates to tribological properties of fatty acids and fatty acids mixtures and aims at providing more information on and better understanding of the wear process in the presence of low-sulfur fractions containing these substances at very low concentration under boundary lubrication conditions in the steel-on-steel system.

Experiments were carried out using a ball-on-disc friction machine. To get detailed information on interaction of diesel fuel components with individual fatty acids and mixtures of acids, low-sulfur diesel fuel cuts as well as their mixtures and two model hydrocarbons were used as the base fluids.

Although the overall picture of the obtained results is very complex, it can be concluded that: (a) Tribological properties of base diesel fuels are determined by the highest boiling fractions and heterogeneous compounds present in these fractions; (b) Fatty acids and their equimolar mixtures - added to the „reformulated diesel fuels” at the adequate concentration - show excellent antiwear properties; (c) Both the chemical structure and viscosity of base fluids influence the wear behavior of fatty acids and their mixtures.

All the findings are challenging from the view-point of their interpretation as well as from their relation to the diesel fuel constitution. Obtained results also evidently confirm the complexity of the boundary lubrication approach.