Vegetable oil is an agricultural product, which can be processed as biodesel. Biodesel is an alternative fuel to substitute diesel oil, which used as diesel machine. The process of biodesel involves cost and through long process. It needs to know the characteristic of the vegetable oil before it is processed into fuel. The aim of this research is to discover the impact between mixture of heated-castor oil and heated-coconut oil, which can be used as fuel. This research is conducted by mixing castor oil and coconut oil with comparison of composition as 100%:0%, 90%:10%, 80%:20%, 70%:30%, 60%:40%, 50%:50%, 40%:60%, 30%:70%, 20%:80%, 10%:90%, 0%:100%, composition ratio 50%:50% there are 3 samples. The oil is heated to 120 degree celcius in 30 minutes, for a 50%:50% composition ratio heated for 30 minutes of sample 1, 60 minutes of sample 2 and 90 minutes of sample 3. Based on the castor oil test contained unsaturated fatty acid, which was 41,59% linoleic. Coconut oil contained saturated fatty acids, which was 47,68% laurate. The more increasing of the coconut oil towards castor oil percentage, density, viscosity and flash point the castor oil could decrease, except the heat value become mount. The heating process towards the mixture of castor oil and coconut oil with long duration, can increase the density, viscosity and flash point. The heat value tends to increase, but on the test with a long duration, that is 90 minutes the heat value decreases.