Both acrylic and oil are two valuable techniques of painting. Both have their own advantages and properties but they are far different from each other. It is the dream of every artist to create artwork in an easier, more convenient, and better way. It can be possible if you can work following some simple steps.
Mixing both of them is a good idea but there are some points which you have to remember. The first thing that you have to remember is that oil paints are oil based cannot work with water.
Second thing is that acrylic paints are water-based and cannot get stable over oil. You can perform an experiment by yourself: take a bowl of water and put oil in it. Try to mix oil in water which is not possible. Same in this case, acrylic cannot be mixed with oil.
But
There are always some alternatives that can be used to get the same results. You cannot mix them but you can combine them on canvas. Well, there is also a thing to note you cannot do acrylic over oil because water cannot be stable over oil. But, you can do oil over acrylic by following some strategies.
Follow the link to get the complete method of painting oil over acrylic.