Define bad anyway. There can be oil that meets basic standards and isn’t as good for a specific engine or use case as other oils. Even “good” oil has a definition. Good enough? Good as in optimal? Vehicle makes it to 200k, 500k, a million miles? How many of those miles are a function of oil choice? Etc etc There are so many ways to slice this topic. Depends on your goals and what function is attempting to be defined.