if the oil looks like chocolate milk and or fills itself up (meaning, the dipstick shows at the add mark, then sometime later WITHOUT having added oil it shows at the full mark OR anywhere else above the add mark.) Rust on the dipstick.
are all indicators of coolant getting into the oil.
also white "smoke" out the tail pipe (not gray or black) indicates a lot of moisture in the exhaust system ( think what you get on a cold morning when you start any car up)