Comparative analysis of the lubricating power between a pure mineral oil and biodegradable oils of the same mean iso grade

n this paper, we compare the viscosimetric and tribological properties of some vegetable oils and one synthetic ester with a pure mineral oil. The viscosimetric characteristics of lubricants show that both vegetable oils and ester have a higher viscosity index than mineral oil. The test results show that all tested oils have a somewhat dilatant behaviour.The oiliness, antiwear and extreme pressure properties of lubricants have been studied respectively with a Stribeck machine and a four-ball machine.
We have noted the following: On the four-ball machine, extreme pressure results expressed in terms of pressure wear index and mean hertz load show that the higher performance is obtained with the vegetable oils. Extreme pressure results expressed in terms of weld load, do not show a big difference between the tested oils. Antiwear results expressed in terms of wear scar show that die highest performances are obtained with vegetable oils. On the Stribeck machine, oiliness results expressed in terms of friction coefficient indicate that:
in the regime of fluid lubrication, tested oils have me same behaviour; in die boundary lubrication regime, both vegetable oils and synthetic, ester have a better response uian mineral oil.