A method of increasing oil pressure in a heavy duty truck engine lubricating system is provided. The lubricating system comprises an oil pressure regulating assembly mounted in an oil filter base and having a main spring to regulate oil pressure, and a high pressure relief valve assembly mounted in the oil filter base and having a peak clipping spring to relieve oil pressure when the pressure exceeds a specified limit. The method includes the steps of replacing the main spring with a replacement main spring having a higher spring constant and replacing the peak clipping spring with a replacement peak clipping spring having a higher spring constant. A replacement kit for increasing oil pressure is also provided.