abstract
- © 2019 Elsevier LtdThis work aims to determine the alteration of lubricity properties of Jatropha oil (SJO) due to thermal ageing caused by approached long-term use conditions as lubricant in engines. SJO, a mineral engine oil (EMO) and a blend made of 80%vol. of EMO and 20%vol. of SJO (B20) were tested. The oils were thermally aged at 160 °C for 30 and 60h. Oil ageing was characterized by measurement of oxidation, depletion of additives, kinematic viscosity and viscosity index. Ball-on-disk tests were conducted to evaluate friction coefficients and wear rates of disks samples from engine cylinder liners by using the oils. SJO was seriously oxidized compared to EMO and B20 by ageing, exhibiting high changes of viscosity from 58.8 to 1970 cSt at 26 °C and decrease of viscosity index from 262 to 200.4. The friction coefficients of SJO were not altered remaining in low values 0.06¿0.07. The viscosity increase allowed a reduction of wear rates from 0.00065 to 0.0002 mm3/m. B20 exhibited better lubricity properties than EMO; and they even were improved after ageing. Thus, SJO could be blended with mineral oils in low concentrations to reduce friction and wear while promoting safe use of a renewable product in short and long-term uses in engines.