Ingersoll and 15T2 lub oil turning milky, why??

Sogyer:
The milky appearance of the oil is due to moisture (water) getting into the oil. I recommend that you drain and change the oil immediately. atmospheric variations (particularly high humidity) will cause this. There are two reasons. First, when the compressor is running, air coming through the air intake will have water particles in it. That moisture in the air slips past the piston rings and accumulates in the crank case. There's no stopping that, but a clean air filter will help. Secondly, while the compressor is running, it tends to heat up. Any moisture that has entered the crank case will vaporize due to the increased heat of operation. When the compressor is shut down, the moisture vapor will condense on the inside walls of the crank case and form droplets which will run down into the crank case oil. When the compressor is started again, the oil agitators at the bottom of the pushrod caps will agitate the oil, thusly mixing the condensed water with the oil causing the milky appearance. Best to check the oil at each start-up, and change it when it gets milky.