It is recommended to change the oil in your vacuum pump on a regular basis, typically every 3-6 months, or as specified in the manufacturer's guidelines. This helps to maintain the pump's performance and prolong its lifespan by preventing the build-up of contaminants and reducing wear on the internal components. Additionally, changing the oil can help to improve the pump's ultimate vacuum pressure and reduce the risk of pump failure. It is important to use the correct type of oil for your specific pump model, as specified by the manufacturer, and to follow the recommended oil change intervals to ensure optimal performance and longevity of your vacuum pump.