Lubricity

The lubricity property of diesel shows its ability to minimize friction between surfaces in relative motion under load conditions. When lubricity is insufficient, many internal engine components, including fuel pumps and injectors, are prone to excessive wear and metal damage. This results in a shortened service life and high replacement costs.

Diesel has good natural lubricity. However, the introduction of ultra-low sulfur diesel (ULSD), with a maximum sulfur limit of 10 mg/kg achieved by a hydrodesulfurization process, has resulted in a loss of inherent lubricity.

While sulfur is not directly linked to the lubricity of diesel, the lower lubricity levels in ULSD are a direct effect of the refinery process used for desulfurization. To increase lubricity values, refiners usually add