Biodiesel is a mixture of fatty acid esters which can be produced from vegetable oil or animal fats with methanol. Biodiesel is a very promising alternative fuel to traditional petroleum-based fuels, as it is nontoxic, renewable, and has better emission characteristics. A major barrier to the wide-spread application of biodiesel is its high production cost, which can be attributed to the high cost of refined oils as raw material. Crude oils are potentially a much more economical source for biodiesel production, and can increase the availability and diversity of oil feedstock. However, waste oils generally contain significant amount of free fatty acids (FFA) and water, and have to be treated by a two-step process which involves the use of strong acid (H2SO4) to first esterify FFA, followed by the use of strong base (NaOH) to transesterify oils. These traditional homogenous catalytic processes are corrosive and can generate a large amount of waste water. Moreover, these homogeneous catalysts cannot be easily recovered. In this study, a single-step method for simultaneous transesterification and esterification over heterogeneous metal oxide catalysts was developed. The effects of metal oxide molar ratio, calcination temperature, FFA concentration, and water content on the yield of fatty acid methyl esters (FAME) were investigated. XRD, XPS, BET, SEM and EDS were used to characterize the structure of catalysts and the nature of active sites. Using a 3:1 molar ratio of mixed oxides, a high yield of FAME can be obtained using crude soybean oil, crude palm oil, waste cooking oil etc. as feedstock.