The influence of oxygenates on lubricity of fuels for CI engines

Lubricity of fuels for CI engines becomes one of very important parameter since the sulphur content was decreased to 50 and actually 10 ppm. To provide effective lubrication of fuel pumps and unit injectors elements, in case fuel does not contain organic sulphur compounds, the oxygen containing organic compounds are added as lubrication additives. Biocomponents are usually introduced into mineral diesel fuel containing additives package, which includes lubricating additive (organic acid). The aim of this paper is investigation of the influence of polar oxygenates added to petroleum diesel fuel in concentration between 5 and 20% (V/V) on lubricating additive effectiveness in protective layer creation. The results of HFRR tests obtained for blends of commercial diesel fuel containing lubricating additive with biobuthanol models (MB) leads to conclusion that: − generally the buthanol isomers addition increases wear of upper ball of HFRR apparatus, − wear of upper ball of HFRR apparatus depends on the average film thickness and does not depend on tested fuels viscosity at 40°C, − dilution of commercial diesel fuel by biobuthanol models and consequently decreasing of lubricating additive concentration cannot be the only reason of deterioration of tested blends lubricity. It was concluded, that the possible reason of lubricity deterioration by buthanol added to commercial diesel fuel in concentration between 5 and 20% (V/V) are antagonistic interactions between oxygenates (buthyl alcohol) and lubricating additive. These antagonistic interactions depend on the structure of buthanol isomers.