The Brazilian as well as the global energy matrix is still mostly supported by non-renewable energy sources such as oil. However, the national energy scenario has a much higher renewable share, and this behavior is largely due to the fact that the country has abundant renewable resources. The immediate availability of renewable grease in Brazil fell on soybeans, the main Brazilian agricultural crop. However, reliance on a single source, whose oil yield per planted area is low (approximately 500 kg/ha), led to the need for alternative sources with higher energy density. Thus, this work sought to obtain biodiesel through frying oil mixed with castor oil in order to obtain biofuel with adequate physicochemical properties and reducing dependence on soybean oil. The physicochemical analyzes, as well as statistical tests revealed that among the obtained indexes, the acidity and the viscosity were above the value established by the National Petroleum Agency (ANP), while for the iodine index a positive effect of the addition of castor oil was registered, indicating effectiveness regarding the strategy used. The value of the acidity index with the addition of castor oil to the frying oil was 0.49 mg KOHg-1 and the viscosity value was equal to 7,02 mm(2)/s which was within the norms established by ANP, EU and ASTM. The value of the iodine index was 108.3 g/100 g of iodine, remaining within the EU standard, while without the addition of castor oil these two indices were not within the mentioned standards. (C) 2020 Elsevier Ltd. All rights reserved.