@ia_camper is correct. You’ll hear just as many people say they work as they don’t work. And there’s no evidence they do other than anecdotal. Peppermint oil and chili oil have been tested to be effective, but really the only way to keep mice out is to seal off all entry points, which I detail here: https://camperfaqs.com/how-to-keep-mice-out-of-camper-best-methods
