I ran across a series ten-ish years ago at a yard sale and just read the first few pages of the first book and now I want to find them and read them. The main character was a woman who had her own auto repair shop. She could sense when a supernatural being was nearby and identify them. She recognizes a young man who shows up as a werewolf and begrudgingly agrees to hire him despite him not having papers. Her first order of business is to make him go eat, because she can tell he is hungry enough that he is having trouble controlling his wolf.
That is a really good summary of the "Mercy Thompson" series starter by Patricial Briggs.
Patricia Briggs - Wikipedia.
Mercedes Thompson is a skin walker raised by werewolves, who runs a one-woman auto mechanic's garage in contemporary Kennewick, Washington.
I cannot find my copies right now, so I can't tell you if you want the 1st book or one of the later ones.
Could it be the Elfhome series by Wen Spencer?
The first book is Tinker.
Inventor, girl genius Tinker lives in a near-future Pittsburgh which now exists mostly in the land of the elves. She runs her salvage business, pays her taxes, and tries to keep the local ambient level of magic down with gadgets of her own design. When a pack of wargs chase an Elven noble into her scrap yard, life as she knows it takes a serious detour. Tinker finds herself taking on the Elven court, the NSA, the Elven Interdimensional Agency, technology smugglers and a college-minded Xenobiologist as she tries to stay focused on whats really important her first date. Armed with an intelligence the size of a planet, steel toed boots, and a junk yard dog attitude, Tinker is ready to kick butt to get her first kiss.