No offense meant to anyone here who is in HR in any capacity, but it's been my experience that if you show me a room full of Mensa members, I'll show you a room that has no HR people in it. Often they are looking for the "soft skills" type stuff, not the specific knowledge/technical aspects of the job. She probably wont ask you much about cars, because she probably lacks the knowledge to know if your answers are full of crap or not. She'll probably be looking more for a positive, can-do attitude than anything else.
When they ask if you have any questions, it is NEVER the correct answer to say no. Do research and ask something, anything, even if you know the answer to it. The point is to show you have taken the effort to do your homework.
One question that I've always gotten good mileage out of is "What are the common denominators of the most successful people at this company." For some reason, HR types just eat that stuff up. I often get "wow- thats a really good question, I've never been asked that before".