This work aimed to produce a biodiesel from oils used in restaurants of São Paulo, Brazil, to discover the power production city and to demonstrate its economical feasibility. For this, it has been researched in the Brazilian market sales prices of glycerin, carbon credit, biodiesel and diesel blend, well as well, the amount of B20 blend (70.1 103 m3/month) used by the bus fleet of São Paulo and the amount of residual oil generated by restaurants. During the collection of frying oil samples used in restaurants, it has applied a standardized questionnaire (1-5 Likert scale) to the manager, in which contained questions about the type of restaurant, the amount of frying oil produced and if he knew the environmental impacts of its disposal. Ethanol was mixed at 1:7 to the samples of cooking oils collected from restaurants and it was transesterified at 60 °C, for 1 h, in order to obtain biodiesel, using NaOH as a catalyst. Results showedthat the restaurants had a monthly consumption of 120 L, giving 3.6 103 m3/month; it is equivalent to 48 %of B100 used in bus fleet. A conversion yield of 87 % has found in this work and with its production is possible to reduce US$ 120 million per year the fuel cost. Also it is possible contribute to the reduction or elimination of indiscriminate disposal of oils; of 92 % of sulfur emissions and to acquire the carbon credits which improve the city's image as it becomes an environmentally friendly city.