I used to worked in metal industries. Threading/tube milling machines are all uses oil base coolant. It can lubricate the steel sheet, to prepare it for formation.



Oil itself is none corrosive, however rubber is degradable by oil. That's my worry. I strongly advice you to atleast drain your radiator replace with clean water without additive. Run for a few days and flush again with clean water. Repeat the same step for 2 ~ 3 times without additive, you should be safe. I do not recommend radiator flush by using chemical, car already 7 years old. When doing chemical flush, at the same time risking to melt your radiator. Clean water is sufficient, make sure you change it frequently. Until you're satisfied with the result, then you can put additive