Ans: Proper care for your 5.9 Cummins includes routine oil changes. It ensures maximum wear protection without harming the engine. The oil change intervals vary between the different versions of 5.9 Cummins. For a 5.9 Cummins 12 valves, you should change the oil every six months or 6,000 miles. For 5.9 Cummins 24 valves, change the oil after 7,500 miles or every six months.