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Abstract: In this experimental work, the viscosity and density of methyl ester based waste cooking vegetable-biodiesel oils were investigated under varying temperature and blend ratio of ultra-low sulfur diesel summer (ULSDS). The transesterified fatty acid methyl ester of waste cooking vegetable oils collected from local restaurants and cafes was used as neat biodiesel. Six different fuel blends (5%, 10%, 15%, 20%, 50% and 80% by volume mixing with base biodiesel) were studied along with base ULSDS fuel and pure biodiesel. Tests for viscosity and density were performed in the temperature range -13℃ -90℃. It is found that pure biodiesel has the highest viscosity and density at a given temperature among biodiesel blends. Moreover, the density of each fuel sample decreases linearly with the increase in temperature. On the other hand, the viscosity decreases exponentially with the increasing temperature of each fuel sample. Moreover, the objective of this experimental work was to study the changes in the properties of biodiesel and the mixtures of the biodiesel with ULSDS during the long-term storage. The fuel samples were stored for 12 weeks at constant temperatures (40℃±1) and properties such as kinematic viscosity and density were periodically measured. The observations of the sample were tested every two weeks for a period of 12 weeks. Based on the experimental results, kinematic viscosity and density were increased upon extended storage by only small increments.

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