When I drained the brown stuff out some got on the concrete, I washed it off with water and it left a nice sheen like oil would so I suspected oil. There is also a slimy residue floating on the water in the overflow tank. Is this the additive? Maybe I need to flush it a couple times. I did notice a small coolant leak down by the transmission so I suspect a heater valve connection or a bad heater core although I have no leakage in the cabin or any smell of anti-freeze in the car.

I have seem many posts about oil in the coolant but no coolant in the oil and not sure how this is possible......