If there is oil in the coolant, you need to check two things. First, if the vehicle has an automatic transmission, it is possible for the trans cooler, that is part of the radiator, isn't leaking and allowing trans fluid to get into the radiator as well as coolant getting into the trans. Check the trans level and condition of the fluid. Next, with a bad headgasket, motor oil can get into the coolant and coolant into the oil. Check motor oil for condition. If both are clean and full, flush the cooling system and refill with new coolant. Drive it for a few days and check it again to confirm that there is contamination and not just dirt from old coolant. If there is oil again, then you need to check for a bad head gasket.

Answered by Jacobandnickolas (expert)
57,318 answers provided