The ideal oil pressure at idle varies depending on the car brand and model, but generally, it should be between 20-30 PSI for cars and 25-35 PSI for trucks. However, some sources suggest that the oil pressure should be at least 10 PSI at idle and about 10 PSI per 1,000 RPM, with it maxing out around 60-80 PSI. It is important to note that oil pressure can vary depending on factors such as the size of the engine, the diameter of the bores, and the viscosity of the oil. If the oil pressure is below or above the recommended range, it is considered too low or too high for the engine, which could be harmful to the engines longevity. It is recommended to check the vehicle manual to know the specific oil pressure range for your car model and engine type.