I know a few women that work in an automotive field (one at a local auto parts store) and she is quite knowledgeable. Like previously said, sometimes I will go straight to her because she doesn't try to sell you something you don't want/need, she just gets you what you want right off the bat.

My dad did have one rather bad experience with women in the automotive field though....
He was at work (he works at a diesel shop where they do all kinds of stuff....literally) and was changing wiper blades and some other stuff on a truck. Had the wipers pulled away from the windshield and the blades off while he went to get the new blades. Well, one of the other mechanics there, a female, was going to pop the hood and begin work on the other things that needed done to the truck. She ended up opening the hood while the wipers were up and the hood hit them and they slammed back into their original position against the windshield....cracking it in the process.
Now, I suppose it could happen to anybody, but he came home that night and was going on about how somebody could be that stupid to open the hood with the wipers up. She still works there though and I haven't heard any other bad stories about her other than that one.