My wife tells me the same thing. Although I wouldn't call me love for cars and obsession. Its a hobby just like her shopping. She understands that and she enjoys cars shows and races with me as I take her shopping. Its a two way street. I agree with dramaqueen, don't be so selfish. Its ok to love cars and always want to talk about them, but what about her? if you care about her at all you will shut up and listen sometimes, its the least you could. Or you could just find a girl that loves cars too!!
in one of her quotes you put she said she dosen't like talking about cars because she dosen't know about them, why can't you teach her? Explain to her how they work and why you love them, maybe she will come around.