Waste cooking oil from the university cafeteria was used as feedstock to produce biodiesel. The feedstock was then converted to biodiesel using two different methods. The two methods tested were with and without pre-heating to study the effect of preheating on biodiesel. For each one of the two methods two types of catalysts were used that is alkali and acidic. The effect on biodiesel yield, calorific value, viscosity, and density was observed. It was found that with preheating to higher temperatures, the yield was 87% with alkali catalyst and 70% with acid catalyst. On the other hand, without preheating, it was found that the yield using alkali catalyst was 98% and 75% using acidic catalyst. Further, the highest calorific value was obtained using alkali catalyst without preheating.