Explore the possibility that the engine oil is not getting hot enough, long enough to boil off the moisture in the oil. Cover the oil cooler air inlet, and monitor the oil temperature carefully for a long flight (more than an hour). Get the oil nice and hot, but not overheated. If the oil temperature will stabilize at 190F to 205F, and is within the limits for the engine, fly it around for an hour or so that way, it'll help. A short flight, or circuits is not good flying for the engine in those conditions.
The 182RG I used to fly a lot always had milky oil. We tried everything, it was always milky. The plane always ran very well for many years, so we did not worry about it too much...