I Accidently Put Engine Oil In My Radiator – Now What Do I Do?

Reader Question
Hi Austin,

I put engine oil in my radiator (Ford 1996 F250 7.5L) by mistake (both the oil and radiator fluid were in a blue container and I grabbed the wrong one).

I flushed it out and refilled and have not seem to be having any problems except that there is a constant build up of oil inside the radiator by the top of the neck where you take the cap off. Should I flush it again or just leave well enough alone? Thanks,

Hi There Mark,

I know the feeling. I get at least one email a week from people doing things like this. I think you are ok, especially since you already flushed it. I would take a paper towel and try to soak up the oil that comes to the top. Oil and coolant don’t like each other, so the oil will always float to the top. You might see oil returning there for awhile, as it makes it way to the radiator neck.

If you start to see the oil looking like a muddy milkshake (not just droplets of oil floating on top of coolant) I would take the truck to a fast lube place and have them flush the cooling system with their flush machine.


Austin C. Davis

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