Hello,
Typically there is something in the schema for each branch of the "oneOf" that is unique to that branch. For instance, a field "vehicleType" which is {"enum": ["car"]} in one branch and {"enum": ["jet"]} in the other. That prevents any instance from matching both.
Alternatively, if your types really overlap like this with no way to distinguish them, you might be fine with "anyOf".
thanks,
-henry