Head gasket
Cracked head
no but antifreeze in oil will eat the bearings
No, oil is lighter than antifreeze.
Cracked injector cups.
NO! Take it to a mechanic immediately. Call AAA at once, if you are a member. Oil is not antifreeze and antifreeze is not oil!
Could be water or antifreeze getting into the oil
most likely a blown head gasket.
Odds are you have blown a head gasket and the antifreeze and oil flow share the same gasket. As the gasket wears, the antifreeze mixes into the oil and vice versa! I suggest replacing your current antifreeze and do a full flush. Test it for a few days and test if you have oil again. A tell tell sign of a blown head gasket is black smoke (burning oil) or white smoke (burning antifreeze ) coming out the exhaust.
cracked head or bad gasket
YES
Look at the oil on the dipstick. If you have antifreeze leaking into the crankcase the oil will be milky.
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 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.