In this paper viscosity index of coconut oil was determined using three methods. Viscosity index was calculated from the measured viscosity at 40°C and 100°C using ASTM Method D 2270 and was graphically determined using ASTM D 341. Viscosity index calculation was performed with a computer program using kinematics viscosity at 40°C and 100°C. The viscosity-temperature coefficient was calculated from the measured viscosity at 40°C and 100°C. Viscosity index of a coconut oil was determined using a set of Schott Ubbelohde-type viscometers selected according to the values of their constants, so that the margins of the uncertainty, inherent in the Hagebach-Couette correction, does not exceed the error allowed for the measurements. The measurements were carried out at 40± 0.1 and 100± 0.1°C, according to the recommendation of ASTM D2270. Viscosity index obtained with the calculator program is 99,39% lower than that obtained by equation (1). The viscosity index obtained by the graphical method is much higher than that obtained by the other methods. The viscosity-temperature coefficient for coconut oil can vary by a factor of 10 depending on the temperature. The viscosity of coconut oil is dependent upon temperature. Viscosity decreases as temperature increases because the molecules vibrate more, and interact less.

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