Be aware that the oral committees do not make a decision on whether you pass or fail. That decision is made later by all faculty in Mechanical Engineering during a special faculty meeting. But the faculty does base its decision on the recommendation of the oral committees, as well as on your performance in the written exam. The oral committees do not know your scores in the written exam.
Each of the three committee member has 15 minutes to question you. They will ask the same questions of each candidate. Your advisor is allowed to be present but is not a member of the questioning committee.
Other committee members or your advisor might interject questions or try to rephrase a question if they think you may be misunderstanding it. If you feel you are getting confused by having to respond to too many questions, please ask your chairperson whether you can have a bit of time by yourself to think through the question. Also, do not be afraid to ask the committee member to rephrase the question.
After the exam, you should leave. The committees will discuss how you performed; however, you will not be informed of the results at this time. Since the oral committees do not make a decision, but only a recommendation to the combined faculty, the chairperson will not divulge the recommendation. The decision of the combined faculty may well be different from the recommendation. Do not ask your advisor, he/she cannot tell you either.