Sounds like coolant in oil, most likely a head gasket issue.pull the spark plugs and the one that is the cleanest will indicate the offending cylinder. But with that you may or may not see white exhaust. Another and more probable cause would be a coolant leak in head gasket from a coolant passage across to a oil return passage. A cracked head or block, would do that as well as a warped head but it would have to be an extremely bad warp.pressure test the cooling system and if it wont build and hold 12-15 psi then you have a serious problem.
