This study aims to determine the effect of microfiltration and transesterification treatment of floured sardine used frying oil on the acid number, viscousity and composition of methyl ester on the biodiesel produced. There are 2 variables in this study, the first variable is the size of filter paper with 2 levels of treatment, while the second variable is the percentage of NaOH in sodium methoxid used in transesterification with 3 levels of treatment. The study was conducted with 3 repetitions, so that 18 treatments were obtained. Acid number and viscousity values refer to SNI Biodiesel no. 04- 7182-2015. From the results of the study, the acid number values of all treatments were included in the limits poured in SNI Biodiesel no. 04-7182-2015 namely Max acid value 0.5 mg-KOH / gr but in this study acid ranged numbers were obtained from 0.26 to 0.33 mg-KOH / gr,viscousity based on SNI is 2.3 - 6.0 mm2/s in this study obtained biodiesel viscousity with ranged from 3.5 mm2/s up to 16 mm2/s. The highest methyl ester content was obtained in the treatment of 16 µm microfiltration and 1.5% NaOH concentration in the transesterification treatment, producing methyl ester of 100%, with the composition of methyl ester including Octanoic acid 10.497%, Decanoic acid 7.393%, Nonanoic acid, 9-oxo- 1.468%, Dodecanoic acid 12.241%, Tridecanoic acid, 12-methyl- 18.630%, Pentadecanoic acid 13,835%, Hexadecatrienoic acid 1,846%, 9-hexadecenoic acid 33,180% and Hexadecanoic acid 0.910%.
