I have a milky residue inside of oil cap but no water mixture in oil itself what

Could be condensation from weather changes, not driving far enough for the engine to reach full operating temp. Check for white smoke coming from exhaust, and watch your coolant level. Have a coolant pressure check done if your really unsure.

I say no problem! Condensation, warmer in the day colder now at night! Keep a check on the coolant level. Good answer #1. Must have been pecking about the same time!

First try to flush, and clean the system. If you still have a milky substance it could be a lower intake manifold gasket.

I also agree with #1