Online peer-to-peer car sharing services are increasingly being used for enabling people to share cars between them. However, our body of knowledge about peer-to-peer car sharing is still limited in terms of understanding actual use and which opportunities and challenges present for those who use them. In this paper, we investigate peer-to-peer car sharing between car-owners and car-borrowers as facilitated by the Australian car sharing service Car Next Door. We conducted a study with 6 car-owners and 10 car-borrowers. Our findings, outlined in four themes, suggest that P2P car sharing fuels different goals for both borrowers and owners. While it is complementing traditional means of transportation car sharing is also in itself a mean of mobility, for example, for recreational purposes. Further, the sharing service plays a central role in supporting the users to make it more convenient to share cars, for example, by letting borrowers find and book cars instantly reducing resources needed to borrow a car. We further discuss our findings and relate it to existing literature providing opportunities and challenges for future research and design on car sharing in HCI.