The main challenge in today's modern diesel engines is to design the parts, which should withstand higher temperatures. To achieve this, selection of materials and tolerances are very important. The product identified for this study is an oil pump, which is an engine auxiliary component. The function of oil pump is to supply oil to different parts of the engine to lubricate and reduce the overall engine friction. The different speed and load condition for which the engine is subjected pose a challenge to the oil pump, to supply necessary quantity of oil at required pressures. Normally, the oil pump is subjected to a temperature of 120°C at higher speeds. However, the peak oil temperature in modern diesel engines can be as high as 140°C. When the existing pump was tested at full speed and suddenly decelerated to idle speed, it was observed that the minimum oil pressure was not maintained for engine lubrication. With this new demand, the existing oil pump needs to be modified to work at elevated temperature maintained minimum oil pressure for the above said requirement.The oil pump selected for this study, is positive displacement type gerotor pump. In our previous study , the key design parameters, clearance and rotor thickness were identified for improving the pump performance. Steady state tests were performed with different combinations of axial clearance and rotor thickness. From the experimental results, it was observed that the impact of both axial clearances and the rotor thickness are critical to achieve the target oil pressure. The combination of the clearance and rotor thickness increased the flow rate at idling speed by 7% at 140°C compared with existing design. Though the pump performance improved, the power consumed by the pump also increased marginally. To counter the increase in power consumption, the external diameter of outer rotor was reduced. The modified design was also tested in actual engine and an improvement of 11 % in oil pressure at idling speed was observed. This modification has also improved in reducing the priming time at cold start conditions.