Milky oil on the dipstick can indicate an engine problem. If noticing milky looking oil on the dipstick, then the first thing to check is the engine’s coolant. A leaky head gasket can allow coolant to pass into the oil system. When coolant and oil mix, or attempt to mix, the result is oil that looks milky. However, this can also be caused by a collection of moisture created by combustion. This type of moisture builds up because the engine was not allowed to reach, and maintain normal operating temperature. The latter can be fixed by properly warming the engine, while the former requires a new gasket.
For more info, see How to Check Engine Oil Levels