In the present work, different types of castor biodiesels were synthesized by using slow pyrolysis process of raw castor oil in the presence of different types of catalysts. These catalysts as anhydrous sodium hydroxide (NaOH), alumina (Al2O3), sodium carbonate (Na2CO3), potassium hydroxide (KOH) and molecular sieve catalyst zeolite (ZMS-5) combined with anhydrous sodium hydroxide (ZMS-5 combined with NaOH) were used for yielding these biodiesels. So, the effects of variation of the catalyst type and its concentration on both yield of castor biodiesels and the pyrolysis temperature ranges were investigated. It was noticed that through the pyrolysis process, two grades of synthesized biodiesels were obtained in the presence of different types of catalysts. The first at the start of the pyrolysis was yellowish one, termed as Castor Biodiesel Number 1 (CBD1). And the second type was brownish biodiesel, called as Castor Biodiesel Number 2 (CBD2), while the rest was the black and heaviest, termed as bio-mazot. It was found that the highest total yields of biodiesels were obtained in the presence of 1% by volume of both NaOH and ZMS-5 combined with NaOH. Thus, four biodiesels were yielded and termed as CBD1(h), CBD2(h), CBD1(hz), CBD2(hz). And the different physical properties of these four biodiesels were measured according to American Society of Testing Material (ASTM). Also, the chemical compositions of these four biodiesels were determined by using Gas Chromatography Mass (GC-Ms) spectrum as well as the functional groups using Infra-Red (IR) spectrum. In addition, the performance of a single cylinder four stroke direct injection compression ignition engine fueled by two different blends as 5 and 10% by volume of CBDh and CBDhz with gas oil was measured. Thus, the main conclusion was derived from both physical and chemical investigations as well as engine performance that these synthesized biodiesels could be used as a good alternative of gas oil. (C) 2017 Elsevier Ltd. All right's reserved.