That is a great point. I am not sure. Smells like oil but its so tainted with antifreeze who knows. The engine oil is crystal clear and as I said, the car runs great fast smooth and cool. How does the transmission oil get into the coolant?

It looked like I saw transmission lines going into the radiator as if there is core dedicated to the transmission cooler in the radiator as in my GMC Sierra. Please share your story.