A bad head gasket can do that or an engine oil cooler gone bad in the radiator. The year, make and model info would help.
bad head gasket
HEadgasket failure, internal oil cooler leak.
Antifreeze in the oil of any engine means there is a crack in the head gasket, or worse, in the block.
if there is engine oil in the antifreeze generally indicates a cracked head on the engine
A head gasket is leaking or the Head is cracked.
A bad head gasket is the most common cause of antifreeze mixing in the oil. The antifreeze will dilute the oil and it will eventually cause your engine to seize up.
If there is motor oil in the antifreeze reservoir there is a good chance there is also antifreeze in the motor oil. This condition is probably the result of a bad head gasket or a cracked head. Antifreeze mixing with motor oil is a recipe for disaster for the engine. Have a trusted mechanic diagnose the situation soon as possible to hopefully avoid even more costly repairs.
Look at the oil on the dipstick. If you have antifreeze leaking into the crankcase the oil will be milky.
Blown headgasket or an idiot pouring oil in the wrong hole.
On the oil pan reservoir mounted on the bottom of the engine block.On the oil pan reservoir mounted on the bottom of the engine block.
If it is motor oil in the anti freeze, then it is either a cracked head, cracked engine block, or a head gasket blown. If it is transmission fluid in your antifreeze, then the radiator is leaking from the transmission cooler ----- although usually that would cause antifreeze to be in your transmission fluid.
the engine is burning oil. blue smoke oil white smoke antifreeze black smoke excess fuel
Intake gaskets have failed.