Home › Forums › Stay Dirty Lounge › Maintenance Forums › Oil in my intake manifold ?? › Oil in my intake manifold ?? January 28, 2020 at 7:56 pm #895940 college manModerator The oil is from blow by. which is being introduced from the pcv to the intake. If you want to help the issue, You could install a oil catch can. As an engine ages rings wear. letting blow by to occur.