Most research on biodiesel has paying attention on using plant based oils as feed stocks. The aim of the research is utilize the used vegetable oil methyl ester (UVOME), as a substitute for diesel in compression ignition engine. Used vegetable oil methyl ester is derived through transesterification process by using used vegetable oil (UVO) and methanol in the presence of either Sodium hydroxide (NaOH) or Potassium hydroxide (KOH) catalyst. The UVO, methanol and NaOH catalyst are mixed with various proportions in the reactor and heated up to 60oC at constant speed stirring for 4 hours and cool it for 12 hours to retrieve the UVOME. To get the better yield of Bio-diesel, the various proportions of UVO, methanol and NaOH are taken for producing the Bio-diesel. Then this yield is compared with the same proportions of UVO and methanol in presence of the catalyst KOH. The yield of produced Bio-diesels of BN (Bio-diesel in presence of NaOH), BK (Bio-diesel in presence of KOH) were analyzed. The maximum yield 87% of UVOME (BK) is derived through transesterification in the presence of KOH catalyst by using bio-diesel processor is higher than the yield of UVOME (BN) which is derived by using NaOH catalyst. If the methanol and catalyst concentration are increased in transesterification process, the yield of BK and BN are also increased. The experiments were carried out to investigate the engine performance of used vegetable oil methyl esters and their blends with diesel in varying proportions.