High oil pressure is caused by an increase in the temperature of motor oil. Oil pressure is determined by the rate that oil flows through the internal combustion engine of a car. When oil pressure increases, the flow of oil decreases.
Cars are more prone to an increase in oil pressure when first starting. The engine temperature rises quickly when a car is started, and that causes the oil temperature to rise as well. As the car continues to run, the temperature of the oil will continue to rise unless the pressure relief value regulates the temperature. When an engine overheats, or the pressure relief valve malfunctions, oil pressure rises significantly, which causes engine failure.